In switching from the GCS_North_American_1983 projection to the US National Atla
ID: 114191 • Letter: I
Question
In switching from the GCS_North_American_1983 projection to the US National Atlas Equal Area, there was a substantial difference in visualizing the underlying data. Compare the two projections once again and attempt to make measurements between locations using the techniques learned in lab (To project the data in its original projection go into the Data Frame Properties/Coordinate Systems/Layers/GCS_North_America_1983). Does ArcGIS allow line and area measurements in both projections (Select the area icon, which is next to the line icon, to make area measurements)? Why, or why not, might this be the case? Based on your knowledge of map projections, explain why one projection might be better suited to mapping the continental US.
Explanation / Answer
The measure tool lets you measure lines and areas on the mapYou can use this tool to draw a line (or) ploygon on the map and get its length or area. you can click directly on a feature and get measurement information.
Measure line - Double click to complete the line.
Measure an area - Double click to complete polygon(This is unavailable if your data frame is not usig a projected coordinated system.)
Every map projection causes distortion of shapes, area, directions and/or distances. some projections such as rabinson or winkle tripel are attempt to minimise distortions across the world through some compramise of all those factors.Other projections ( such as UTM and State plane) are designed for focuse areas of the globe in order to keep distortion minimal.
The UTM and state plane measurements both close to each other and give same latitude longitude measurements. The result are close to true measurements
when you use different projection the co-ordinate system is different for different projections. its better to use one projection for both mapping the continental US
if you change the projection the view will be different at different projections.
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