More

3D map with latitude and longitude


I have a 3D map with latitude and longitude details. Is there a way I can take a 2D image (a png image) from 3D model in such a way that my 2D image also have the latitude and longitude as it is in 3d model ?

Can 2D image have the details as latitude and longitude ?

Which software should I use for doing this. Can anyone please point me to some online tutorial if available ?

Thanks,


If you need to georeference a handful of PNG files, you should just do it manually in ArcMap. The Georeferencing toolbar allows you to add multiple control points to align an image.

If you need the process to maintain geographic location through the conversion to 3d and then rendering in 2d, you'll need a 3D software that will maintain geographic coordinates throughout your workflow. I rather doubt there are any packages like that with the capabilities of 3dsMax, but you can do more basic 3d graphics in AutoCAD, Sketchup, and even ArcScene, while maintaining the same coordinates.

Although I don't know of any software that will then allow you to produced a georeferenced rendering…


Based on the comments above I am assuming that your starting point is a shapefile, not a map. Likely a 3D shapefile. @Patric already suggested an array of software that will let you visualize and export such data into a 2D image. If I understand correctly you actually want to export the image with the reference grid (latitude and longitude) as a part of the image. i haven't worked with AutoCAD in a long time but i think you can export your model to an image that includes the reference grid. (plot) This becomes more complex when the reference grid needs to be visualized over a surface.

In ArcGIS the reference grid can be easily added to your map in 2D space (ArcMap) but not so easily in 3D (ArcScene). You will have to create the grid as another shapefile (lines) and then either set it's base height appropriately with the scene or drape it over a surface if you are visualizing it over an uneven terrain.

I know I can export reference grids with models out of specialized geology/mining software but that might be an overkill in this case.

You could use ArcScene (a part of ArcGIS if you have the 3D analyst extension) but it's expensive. Your best bet is probably SketchUp. It's free and it's a fantastic true 3D drawing environment.


I don't think PNG will let you have georeferencing within the file itself. A format like GeoTIFF would include georeferencing. PNG won't. The best you can do is have what I would call a 'sidecar' file - such as a .wld file to specify georeferencing for that file.

If you move the image to the correct place in ArcGIS, I would assume it's creating some sort of referencing of this type.

If you want some software to do this for you, then I use FME (though I do work for Safe Software who develop it). It will read Shape data, let you rasterize it, then write to PNG (with a .WLD file to act as georeferencing).

Of course one other question is what you expect to see in the PNG. Since Shape data doesn't contain any idea of feature colour, what colour will you expect to see in the PNG?


A Latitude/Longitude Puzzle

Students use latitude, longitude, and research on characteristics of different states and regions to solve a puzzle.

Links

Interactive
Website

1. Review latitude and longitude.

Remind students that cartographers long ago created a system of imaginary gridlines for the whole globe. The grid lines are called latitude and longitude. They are measured in degrees.

Project the Lines of Latitude diagram and invite a volunteer to point out the Equator. Ask: What’s the number next to this line? (0 degrees) Explain that locations along this line all the way around the globe are at 0 degrees latitude. Lines of latitude measure the distance north or south of the Equator. Point out the lines to the north, labeled with an “N.” Ask: Which of these lines of latitude do you think are in the northern hemisphere? Which are in the southern hemisphere? How do you know? Have volunteers come to the board and explain.

Project the Lines of Longitude diagram. Ask students to name the location of the prime meridian (0 degrees). The lines of longitude show locations to the east or west of the prime meridian.

2. Name locations on a map of the United States.

Next, give each student a printed copy of the MapMaker 1-Page Map of the United States. Ask: Which lines are lines of latitude? Which are lines of longitude? 

Have students find New Orleans, Louisiana on their maps. Ask: How could we name the location of this city using lat/long—short for latitude and longitude? Have students move a finger along the lines at the point of the city to the margins and explain that it is at 30 degrees N latitude and 90 degrees W longitude. This pair of numbers is called the location’s coordinates. Explain that some sites will not be so close to lines of latitude or longitude, so we estimate based on distance to the lines. For example, Denver, Colorado, is at 40 degrees N, 105 degrees W. The longitude measurement is about halfway between 100 and 110 degrees W.

Ask: For what other places can we name the location using lat/long on this map? Give students an opportunity to work in pairs to select 2-3 sites and identify the lat/long for them. Tell students to set the map of the United States aside—they will use it again later.

3. Have students practice using latitude and longitude.

Give each student a copy of the worksheet Earth’s Grid System. Point out to students that the locations of latitude and longitude on the worksheet map are the same for any map or globe. Have them find Albuquerque, New Mexico on the worksheet. Ask:

  • Along what line of latitude is Albuquerque? (35 degrees N)
  • Which two lines of longitude is it between? (105 degrees W and 110 degrees W)
  • What degree longitude do you think it is, between 105 and 110? (It’s in the middle but closer to 105, so about 107 degrees W.)

Next, look at the MapMaker Interactive together as a class, and zoom in to find Albuquerque. Change the units of measure to decimals at bottom left. Put the cursor on Albuquerque and show students the lat/long measurement at the bottom left. Ask: Is it close to 35 degrees N, 107 degrees W? Explain that information on maps that we use on computers and global positioning systems (GPS) is all organized by lat/long. Depending on students’ math level, have them round the decimals to whole numbers or use the decimals.

Have students complete the worksheet Earth’s Grid System to practice finding locations using lat/long measurements. Check for understanding by reviewing the answers together as a class.

4. Have students apply their learning to a lat/long puzzle.

Explain that students will be using lat/long and some clues to solve a puzzle. Give each student a copy of the handout A Summer Day and have them retrieve the map of the United States from Step 2. Have students work independently to read the passage and follow the directions. Provide access to atlases and geography links such as 50states.com for students’ research.

When students have identified the coordinates, completed their research, and identified the state they think is described in the passage, regroup as a whole class. First, focus on the coordinates that do not match the place characteristics in the paragraphs. Ask students for their ideas.

  • A: Arizona—Students may respond that maple and oak trees are not common in Arizona.
  • B: Montana—Students may respond that corn is not common in Montana.
  • D: Florida—Students may respond that the air would probably not be cool in summer in south Florida, and there would be little need to stack firewood.

Both physical and cultural characteristics of Wisconsin fit the description. Explain that it is important to know where places are, but also to understand what those places are like. Have students complete the rest of the worksheet.

5. Have students create a puzzle with clues using a world map.

As a homework assignment, have students use the provided MapMaker 1-Page Map of the world or another map showing lat/long to create a similar puzzle. Have students identify three locations and write coordinates for each. Then have them use atlases and other resources to create three clues that describe one of those locations. Collect and check the puzzles for accuracy and understanding. Have them exchange their puzzles for additional practice with lat/long and characteristics of different places.

Informal Assessment

Check students&rsquo A Summer Day worksheets and the quizzes they create for the world map for understanding.


Longitude - Latitude HTML5

After several shipwrecks, England decided in 1714 to create an office of longitudes (Board of Longitude) which offered a reward to anyone who could find a way of locating one&rsquos position on land and at sea.

The problem is very complex, and navigators continued to use sextants and other astrolabes to find their location at sea. Wireless telegraphy at the end of the 19 th century, and, more recently, the GPS with its procession of satellites, finally brought a precise solution to this problem.

Every point on the surface of the Earth can be located by two angles, in units of degrees.

Latitude: the angle that varies from 90°S (South) to 0° for points lying on the Equator, then from 0° to 90°N (North) for points that are above the Equator.

Longitude: the angle that varies from 180°W (West) to 0° (the reference meridian, called the Greenwich Meridian), then from 0° to 180°E (East).

Click and drag point P on the right hand map in order to change locations.

Click on the Earth and drag it to make it rotate.


Hands-on Activity What's Wrong with the Coordinates at the North Pole?

Units serve as guides to a particular content or subject area. Nested under units are lessons (in purple) and hands-on activities (in blue).

Note that not all lessons and activities will exist under a unit, and instead may exist as "standalone" curriculum.

TE Newsletter

Figure 1. (left) A view from the NOAA North Pole camera. (right) A reading from the North Pole taken on a handheld GPS device. The North Pole is a region of the Earth where a conventional coordinate system such as Universal Trans Mercator (UTM), due to its design, is not as useful. Instead, the Universal Polar Stereographic (UPS) coordinate system is most often used at the North and South Poles.

Summary

Engineering Connection

Coordinate systems and projections are used by many different kinds of engineers that need to understand a project in terms of spatial data. This activity asks students to examine and use known systems in terms of the quantities defined within those systems (for example, degrees, minutes, seconds, meters).

Learning Objectives

After this activity, students should be able to:

  • Identify obvious differences in appearance and accuracy between different global projections.
  • Explain the difference between spherical geographic coordinate systems and Cartesian geographic systems.
  • Demonstrate basic skills in Google Earth such as zooming, locating new places using the search bar, measuring distance, and manipulating multiple GIS layers.
  • Provide examples of how engineers use coordinate systems and projections to help solve real-world problems.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source e.g., by state within source by type e.g., science or mathematics within type by subtype, then by grade, etc.

International Technology and Engineering Educators Association - Technology

Do you agree with this alignment? Thanks for your feedback!

Do you agree with this alignment? Thanks for your feedback!

State Standards
Texas - Math
  • select tools, including real objects, manipulatives, paper and pencil, and technology as appropriate, and techniques, including mental math, estimation, and number sense as appropriate, to solve problems (Grades 6 - 8) More Details

Do you agree with this alignment? Thanks for your feedback!

Texas - Science
  • design and implement experimental investigations by making observations, asking well-defined questions, formulating testable hypotheses, and using appropriate equipment and technology (Grades 6 - 8) More Details

Do you agree with this alignment? Thanks for your feedback!

Materials List

  • computer with a Google Earth installation
  • grid files for latitude and longitude and UTM/UPS from www.earthpoint.us

Worksheets and Attachments

More Curriculum Like This

Students learn about projections and coordinates in the geographic sciences that help us to better understand the nature of the Earth and how to describe location.

Students learn about coordinate systems in general by considering questions concerning what it is that the systems are expected do, and who decided how they look. They attempt to make their own coordinate systems using a common area across all groups and compete to see who can make the best one.

Students explore using a GPS device and basic GIS skills. They gain an understanding of the concepts of latitude and longitude, the geocaching phenomenon, and how location and direction features work while sending and receiving data to a GIS such as Google Earth.

In this lesson, students learn the value of maps, how to use maps, and the basic components of a GIS. They are also introduced to numerous GIS applications.

Pre-Req Knowledge

Students should have some familiarity with Cartesian coordinate systems and basic computer skills.

Introduction/Motivation

Projections are used in GIS in order to take the rounded ellipsoid Earth and make it flat so that it may be mapped. Different projections have different goals in mind. Some are conformal these projections preserve local shape. Others preserve area (equal-area) or distance (equidistant). An example of a conformal projection is the Mercator projection established in 1569 by Gerardus Mercator, while a common equidistant projection is the Sinusoidal projection (Figures 2-3).

It is important in GIS and when looking at paper maps to know the source of these projections, what they claim to represent accurately, and what is known that they do NOT present accurately. In a GIS, one is often zoomed in on a city-size area or smaller. Thus it is not as simple as in Figure 2 to see what distortions of shape, line, area or angle might be present. Yet even if those distortions are not seen, that does NOT mean that they are not significant. When using a GIS to find the distance between neighboring houses or the exact location of a fire hydrant, it is valuable to know the exact location within 2-3 meters. More error than that may result if the account of the GIS projection is either not known or not examined fully as shown in Figure 3.

For more good information, see the article by ESRI. [3] listed in the Referenes section. Also see some very good visual methods to evaluate the level of distortion in a projection using Tissot's Indicatrix, which uses the distortion of a unit circle projected from the globe onto a flat surface, that may be found in Wikimedia Commons. [4] This is especially important to engineers who are trying to gather and analyze data to solve real-world problems, such as the rate at which oil is spreading during an oil spill.

Figure 2. The Earth in two different global projections. The Mercator projection (left) is conformal preserving shape on a small local scale and the Sinusoidal projection (right) is equidistant preserving the accuracy of any linear distance.

Figure 3. The Earth in two different global projections just east of downtown Houston, TX along Buffalo Bayou. On the left is a Mercator projection and the right is a Sinusoidal projection. The yellow arrow indicates the same oxbow lake-like feature being measured in both projections. In the Mercator projection this distance is 492 meters while it is 510 meters in the Sinusoidal projection.

Coordinate systems are important in both concept and practice for geographical information systems (GIS). They serve two main functions. The most important function is to provide a system to uniquely locate any point on the map. That map might describe the surface of the Earth, the lunar surface [5], or the celestial coordinate system[6].

The other important function that coordinate systems provide is that of regionalization. If coordinates have zones (such as UTM) or regions (such as hemispheres in latitude-longitude), then places within those zones can be grouped together for different geographic regions. Again, engineers use this information to gain a better understanding of a specific geographic region that is being studied. For example, an environmental engineering studying a crop field needs to use GIS to understand the layout of that field.

Figure 4. UTM zones across the world. Note that a different projection is used for each of the 60 zones such that the least amount of distortion is in that zone. Then the Cartesian coordinate system applied in the zone (slightly different for each) has the most accuracy.

Geographic coordinates generally fall into two major types of grid systems. Some grid according to the accurate representation of the Earth as a curved surface. These coordinates are like latitude and longitude they assume that the Earth is a spheroid of some kind, and thus when they are projected onto a flat map, they show curvature and non-orthogonality.

Alternatively, coordinate systems such as UTM take the Earth as a projection and place perfectly orthogonal straight lines on top of that projection. In terms of accuracy, the methods that allow curves are better, but from a usability standpoint the orthogonal systems are better. A prime example of a historic use of regular orthogonal coordinates is that of township, range and section as used in the The Public Land Survey System. This system was developed to efficiently divide the American West into land cadastres that could easily be organized and sold to settlers who did not already know landmarks in the area by which to measure property boundaries. [7]

Figure 5. Subdivisions of the rectangular Public Land Survey System showing section, township, and range.

Today we will explore coordinate systems and projections through Google Earth. First, you will look at some different map projections and determine what kind of compromise has been made in the projection to make it look the way it does. The projections are made by experts in GIS and cartography, but anyone who knows even a little about the Earth and its continents and can discern what is happening with these projections.

The second task is in Google Earth. You must open Google Earth and get some specific coordinate systems loaded into your viewer. The first is the standard latitude and longitude geographic system. You will recognize it because it looks like a bunch of lines that are drawn around an orange. The second coordinate system is the Universal Trans Mercator (UTM) system. It looks similar in Google Earth to the geographic lat-long system, but it has lines that are spaced more closely together in the standard UTM zones. Within each UTM zone, the coordinates have a different origin, but the lines are a right-angle orthogonal grid. You should be able to see the difference when you zoom in on the grids such that UTM lines are always right angle, and latitude-longitude lines are slightly off from 90˚ in many cases.

Procedure

  • If desired, adjust the worksheet to involve places of significance to students, such as the location of their school. Then make copies of the worksheet.
  • Make sure that Google Earth is working well on all computers and that the EarthPoint UTM and LatLong grids are working in all aspects (loading lines at different zooms, license issues, turning on and off).
  • Run through the individual exercise completely once so that you are familiar with it on your computers and so that you are able to answer questions better.
  1. Give a first time glance of coordinate systems and projections from what has been given in this write-up or review these concepts after having presented the associated lesson, Projections and Coordinate: Turning a 3D Earth into Flatlands.
  2. Demonstrate (with a computer on a projector if possible) some of the techniques that will be used in Google Earth (zooming, loading the coordinate layers, turning layers on and off, measuring distances) so that students are familiar with it. Consider having a student or two do these steps in front of the entire class with the teacher guiding them.
  3. Give students time to work on their own using Google Earth and the worksheet. Be sure that they understand that the record of their work is what they fill out on the worksheet. Move about among the students, making observations and answering questions.
  4. Continue with Step 3 until all students have finished or class time has expired. Depending on class period length, the exercise may require more than one period.

Vocabulary/Definitions

Cartesian coordinate system: A coordinate system that describes a location based on paired values that correspond to the point's location in reference to a coordinate center. The coordinate center is the intersection of two perpendicular axes which are measured in the same spatial units.

conformal: A geographic projection that preserves only the local shape of a feature.

equidistant projection: A geographic projection that preserve the accuracy of point to point distances on the map but not necessarily shape, area or angle.

map projection: The result of projecting a sphere or spheroid (for example, ellipsoid) onto a flat plane. Projections are sometimes created by mapping the spheroid or a piece of the spheroid onto a standard 3D object such as a cylinder or cone and then unrolling the 3D object so that it is flat.

Assessment

Activity Embedded Assessment

Student Engagement: Walk around to different students' workstations as they work through the exercise. As the opportunity presents itself, have them demonstrate that they can enter in coordinates in Google Earth (GE) and that they are checking to make sure that GE is giving them the correct location. (That is, does your location as displayed make sense as to where you think that you are going?) The questions that students ask you will indicate how well they understand. It is unlikely that they will be able to simply follow the exercise without at least some guidance from the instructor. Their questions about how to do certain parts provide a chance to ask deeper follow-up questions.

Examine the Results: Grade the worksheet with written answers by comparison to the provided answer key. Be sure that the answer key was adjusted to reflect any changes you made to make the questions relate local places. Also, ask students to provide additional engineering examples of when GIS is important to help solve real-world problems.

Copyright

Contributors

Supporting Program

Acknowledgements

This digital library content was developed by the University of Houston's College of Engineering under National Science Foundation GK-12 grant number DGE 0840889. However, these contents do not necessarily represent the policies of the NSF and you should not assume endorsement by the federal government.


Location Mapper (Formerly HB610 Viewer)

While useful for anyone, TCEQ provides the mapper to fulfill House Bill 610 from the 82nd Legislative session. View bill at House Bill 610: 82(R) HB 610

    - Read this first. This downloadable PDF document explains how to use the tools available in the mapper.
  • Metadata - For more details about this data and the Viewer, please visit the Location Mapper Descriptionpage in ArcGIS Online.
  • Access and Use Constraints - This product is for informational purposes and may not have been prepared for or be suitable for legal, engineering, or surveying purposes. It does not represent an on-the-ground survey and represents only the approximate relative location of property boundaries. Presently, all GIS related applications have a statewide exemption from 1 TAC 213 granted by the Department of Info Resources . If you require special assistance, please consult the Esri Software - Voluntary Product Accessibility Templates (VPATs) for ArcGIS Online applications.
  • Contact Us – E-mail the GIS staff at [email protected]

About Setting Geographic Location

Inserting geographic location information to a drawing file makes points within the drawing correspond to geographic locations on the surface of the Earth.

Geographic location information in a drawing file is built around an entity known as the geographic marker. The geographic marker points to a reference point in model space that corresponds to a location on the surface of the earth of known latitude and longitude. The program also captures the direction of the north at this location. Based on this information the program can derive the geographic coordinates of all other points in the drawing file.

Typically a geographic location is defined by its coordinates (for example, latitude, longitude, and elevation) and the coordinate system (for example, WGS 84) used to define the coordinates. Moreover, the coordinates of a location can differ from one GIS coordinate system to another. Hence, when you specify the geographic location of the geographic marker, the system also captures the details of the GIS coordinate system.

Typically CAD drawings are unitless and are drawn at 1:1 scale. You are free to decide the linear unit a drawing unit represents. GIS systems, on the other hand, allow the coordinate system to decide the linear units. In order to map CAD coordinates to GIS coordinates, the system needs to interpret CAD drawing units in terms of linear units. The system uses the setting stored in the INSUNITS system variable as the default linear measurement of a drawing unit. However, when you insert geographic location information, you have the option of specifying a different linear measurement (for a drawing unit).

After you insert a geographic marker in a drawing, you can:

  • Make the program automatically determine the angle of sunlight when you perform sun and sky simulation (photometric studies).
  • Insert a map from an online maps service in a viewport.
  • Perform environment studies.
  • Use position markers to mark geographic locations and record related notes.
  • Locate yourself on the map in real-time on systems that support location sensing.
  • Export to AutoCAD Map 3D, and expect the model to position itself automatically.
  • Import raster files that contain geographic location information and expect them to position themselves automatically (This requires AutoCAD Raster Design).

You can remove geographic location information from a drawing file using the GEOREMOVE command. The geographic marker and GIS coordinate system are removed from the drawing file. However, position markers continue to remain in the drawing file.


GPS Essentials

  • The Universal Transverse Mercator (UTM) is a system for assigning coordinates to locations on the surface of the Earth. Like the traditional method of latitude and longitude, it is a horizontal position representation, which means it ignores altitude and treats the earth as a perfect ellipsoid. However, it differs from global latitude/longitude in that it divides earth into 60 zones and projects each to the plane as a basis for its coordinates. Specifying a location means specifying the zone and the x, y coordinate in that plane. The projection from spheroid to a UTM zone is some parameterization of the transverse Mercator projection.
  • Decimal degrees (DD) express latitude and longitude geographic coordinates as decimal fractions and are used in many geographic information systems (GIS), web mapping applications such as OpenStreetMap, and GPS devices. Decimal degrees are an alternative to using degrees, minutes, and seconds (DMS). As with latitude and longitude, the values are bounded by ±90° and ±180° respectively.

Important to know is that most maps have both UTM and a form of degrees reference. However the ease of use of the UTM is far more efficient then the complex calculations that need to be made to transfer from UTM to Degrees. Almost every recent map uses UTM or MGRS grid. So if you set your GPS settings to UTM and WSG84: both your physical map and GPS are talking the same language. Also you can transfer locations located on the map into your GPS without coverting.

The North Pole

  • True North (also called Geodetic north) is the direction along Earth’s surface towards the geographic North Pole or True North Pole.
  • The North Magnetic Pole is a wandering point on the surface of Earth’s Northern Hemisphere at which the planet’s magnetic field points vertically downwards (in other words, if a magnetic compass needle is allowed to rotate about a horizontal axis, it will point straight down). There is only one location where this occurs, near (but distinct from) the Geographic North Pole and the Geomagnetic North Pole.
    The North Magnetic Pole moves over time due to magnetic changes in the Earth’s core. In 2001, it was determined to lie west of Ellesmere Island in northern Canada In 2009, while still situated within the Canadian Arctic, it was moving toward Russia at between 55 and 60 km (34 and 37 mi) per year. As of 2019, the pole is projected to have moved beyond the Canadian Arctic.

  • Magnetic declination, or magnetic variation, is the angle on the horizontal plane between magnetic north (the direction the north end of a magnetized compass needle points, corresponding to the direction of the Earth’s magnetic field lines) and true north (the direction along a meridian towards the geographic North Pole). This angle varies depending on position on the Earth’s surface and changes over time.

In short: your map is based on the True North, your compass will point to the Magnetic North. Depending on where you are on the planet you will need to adapt your compass to bypass this deviation. Most maps give you the necessary numbers to calculate this deviation. You can also download apps or use websites to know the deviation of a certain location. Best is to know how to calculate it.


Geospatial PDF in Adobe Acrobat: Examining latitude and longitude values

After creating a map with MAPublisher or Geographic Imager, you might want to export it as a geospatial PDF file. You want to ensure that the georeference information of your Geospatial PDF files are correct before bringing them into the field for use. A great way to use geospatial PDF maps (and GeoTIFFs) is to load them onto an iPhone, iPad, or iPod touch with PDF Maps installed.

One way to check for georeference accuracy of geospatial PDF files is to use Adobe Acrobat. Open the “Analysis” tool from View > Tools > Analyze.

Click the “Geospatial Location Tool” from the Analyze panel.

With the Geospatial Location Tool enabled, you can see the latitude and longitude values of the map while you move the mouse over the opened Geospatial PDF file.

An important tip you should keep in mind: you need to set the preference option for this tool correctly depending on the coordinate system of the map in the geospatial PDF file.

Open the Preference dialog window:

Acrobat X on Windows: Edit > Preferences > General …
Acrobat X on Mac: Acrobat > Preferences …

In the Preference dialog window, find the preference category “Measuring (Geo)” from the list of categories.

In the “Measuring (Geo)” category, take a look at the right side. There are many options for the georeferencing tool. One of the options is “Latitude and Longitude Format”. In this section, you have a checkbox option “Always display latitude and longitude as WGS 1984”.

This option is very important. If the coordinate system of the map is “NAD 27 / UTM Zone 16 N”, which geodetic system would you like to have to show the latitude and longitude values in Adobe Acrobat? For example, if you are checking the latitude and longitude values in the WGS 1984 geodetic system, you should keep this option selected. However, if you are checking the latitude and longitude values in NAD 1927 geodetic system, then you should de-select this option. The difference in the distance at the same spot between two different geodetic systems may be small or large. If you would like to see the correct latitude and longitude values, you should be aware of this option.


Geographic Phenomena: Spatial Dimensions

Geographic phenomena are often classified according to the spatial dimension best used to describe their nature. These include points, lines, areas, and volumes (3D). As you likely remember, we used the spatial dimension of map elements (e.g., line vs. point) in the last lab to decide how to symbolize and apply feature labels to our maps.

Points exist in a singular location and thus have theoretically zero dimensions. Points are usually specified using a coordinate pair (x, y) of latitude and longitude, though they occasionally include a z (height).

Lines are one-dimensional spatial features, typically defined by a series of (x, y) coordinates. A z (height) dimension can also be assigned to lines, but this is uncommon. Lines are used to map phenomena that are best conceived of as linear features, including both some features that have greater dimensionality in reality (e.g., rivers) and those that do not visibly exist in the real world at all (e.g., property lines).

Area features are two dimensional and are represented by a series of (x, y) points that enclose a space. Areal phenomena include natural features like lakes and parks, as well as human-defined locations—from continents to census blocks.

2-½ and 3-D features are sometimes grouped together, but the distinction between them is important. 2-½D features define a continuous surface—they have an x, y, and a z at every location. A good example is elevation, which varies continuously across the landscape. Therefore, a topographic map is a common depiction of 2-½D phenomena.

True 3D maps have an x, y, and z, plus an additional data value, at every location. Imagine, as an example, a map of elevation like the one above but at every point along the terrain surface, there are additional measurements being taken at various depths. Thus, rather than depicting a continuous surface, true 3D maps depict a continuous volume.

Keep in mind that the scale of your map has significant influence on what spatial dimension will best represent the phenomenon you intend to map. Cities, for example, are usually drawn as areas on large-scale maps, but appear as points on smaller-scale maps. Rivers are usually drawn as lines on small-scale maps but are better represented as areas on large-scale maps. We will discuss this more during discussions of cartographic generalization later in the course.


Watch the video: ΠΑΡΑΛΛΗΛΟΙ ΚΥΚΛΟΙ u0026 ΜΕΣΗΜΒΡΙΝΟΙ - ΓΕΩΓΡΑΦΙΚΟ ΠΛΑΤΟΣ - ΓΕΩΓΡΑΦΙΚΟ ΜΗΚΟΣ - ΔΙΚΤΥΟ ΣΥΝΤΕΤΑΓΜΕΝΩΝ.HD (October 2021).