Lab 3 Projections

Lab 3 Projections - 44:005 Foundations of GIS Lab 3:...

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44:005 Foundations of GIS Lab 3: Projections The objective of this exercise is to introduce you to the concepts of projection systems and how they are utilized in ArcMap. We will compare distance distortions of two widely used map projections : World Cylindrical Equal Area and Lambert Conformal Conic and we will view the datum shift between the North American Datum 1927 and the North American Datum 1983. The background reading for this lab is in Ch. 3 of your textbook. Overview Measure and compare distance distortions created when you use equal area (equivalent) and conformal conic map projections , reproject dataset in current ArcMap document only Apply a datum transformation to make map layers align, create a copy of the original dataset in the new projection Use ArcMap’s “ On the fly ” projection capability to automatically align datasets Create a map layout using multiple data frames Part I: Distance distortion in map projections 1. Copy the Lab3data to your student folder. 2. Launch ArcMap. Save your document to your Lab3 folder. 3. Add only circle.shp’, ‘cities.shp’ and ‘states.shp’. 4. Move the mouse over the data view window and see the location coordinates that are displayed in the lower right corner of the screen. Degrees-minutes-seconds Decimal degrees These data are unprojected so they are stored in the Geographic Coordinate System. Confirm this by opening the Data Frame Properties, Coordinate System tab. 5. Right click on the data frame Properties Coordinate System. The Current coordinate system should be GCS. In the geographic coordinate system, locations are displayed in longitude and latitude using either DMS units (degrees- 044:005 Lab 3 Pg 1 of 11
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minutes-seconds) as shown above or the equivalent in DD (decimal degrees). Longitude is displayed first, latitude second. In the DD units, positive numbers indicate locations north of the equator and east of the prime meridian, while negative numbers indicate south and west. Working with unprojected data is advantageous for many reasons 1) Distance measurements are more accurate than with projected data. 2) The layer can be easily moved from one projection to another (as we will do in this lab) without creating extra distortion. We will be measuring the distances between various US cities. When using unprojected data such as this, ArcMap uses the latitude/longitude coordinates to determine the distance. We will compare these measurements with distances measured after projections have been applied to see the distorting effects of the two projections. 6. Display city names on the map by right-clicking on the layer name and selecting Label Features from the drop-down menu. 7.
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This note was uploaded on 04/01/2012 for the course 044 005 taught by Professor Davidbennett during the Fall '11 term at University of Iowa.

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Lab 3 Projections - 44:005 Foundations of GIS Lab 3:...

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