Map Projections... Projecting in ArcMap Introduction... Assigning a Coordinate System for your Data Frame All data from DEP/BIS/GIS is stored in the same coordinate system. To display this data, all you need to do is add it to ArcMap. No thought needs to go into whether or not the layers will overlay properly. However, if you have collected data from a variety of sources, you will need to know what coordinate system each dataset uses to ensure ArcMap can display them together. When you add a layer to an empty data frame, that layer sets the coordinate system for the data frame; you can change it later if necessary. As you add subsequent layers, they are automatically transformed to the data frame’s coordinate system as long as there is enough information associated with the layer’s data source to determine its current coordinate system. If there is not enough information, ArcMap will be unable to align the data and display it correctly. In this case, you will have to supply the necessary coordinate system information yourself. ArcMap expects coordinate system information to be stored with the data source. For a layer in a geodatabase, this information is part of the layer’s metadata. For coverages, shapefiles, and raster data, it is stored on disk in a separate file named after the data source but with a .prj file extension. These files are optional files, and you may still need to define the coordinate system for one of these data sources. Note: Changing the coordinate system of a data frame does not alter the coordinate system of the source data contained in it. Map Projections... Using the Projector Mod! Extension Map Projections... Projecting in ArcMap Step 1: Start ArcMap ⇒ Right Click on the data frame and choose Properties. The Data Frame Properties dialog window opens... ⇒ Click the Coordinate System Tab The details of the current data frame coordinate system display in the dialog. ⇒ Click New and Click Projected Coordinate System Step 2: Assigning the Data Frame a Coordinate System ⇒ Type in a New name for your projected coordinate system ⇒ Choose a Projection from the drop down list Enter Values in for the for Parameters… DEP Users enter... False_Easting 400,000 False_Northing 0 Central Meridian –84 Standard Parallel_1 24 Standard Parallel_2 31.5 Latitude of origin 24 Geographic Coordinate System – GCS_North_American_1983 HARN Datum- D_North American_1983_HARN ⇒ Choose the Linear Unit Name from the drop down list ⇒ Click Select ⇒ Browse for the Coordinate System you want your data frame to be in. DEP Users... Our Data’s Geographic Coordinate System is North American 1983 HARN. If you want your data to display in that coordinate system follow the next steps... ⇒ Double Click North America ⇒ Select North American 1983 HARN.prj ⇒ Click Add Your data frame is now set to the coordinate system you specified. ⇒ Click OK The Coordinate System of your data frame has been defined To save the Projected Coordinate System... ⇒ Click Add to Favorites Step 3... Option 1: Displaying Data with a Predefined Coordinate System ⇒ Right Click the data frame that you want to set the coordinate system of and Click Properties. You can have layers with different coordinate systems and projections in your data frame and can change your data frame to any of the coordinate systems or projections your layers are in. Or, you can change your data frame to any coordinate system or projection even if it differs from the ones your layers are in. Again, Changing the coordinate system of a data frame does not alter the coordinate system of the source data contained in it. ⇒ Click the Coordinate System tab ⇒ Double Click Predefined Navigate through the folders until you find the coordinate system you want and click it. ⇒ Click OK All layers in the data frame will now be displayed with the pre-defined coordinate system. Option 2: Importing a data source with a defined coordinate system ⇒ Right Click on the data frame and choose Properties ⇒ Click the Coordinate System ⇒ Click Import Browse to select a data source with a defined coordinate system that you want your data frame to be in. Select a Data Source... ⇒ Click Add The Data Frame has been updated to the selected Coordinate System... ⇒ Click OK Step 4: Modifying Coordinate System Parameters Sometimes you may need to adjust the Projection, Parameter Values or linear ⇒ Right Click on the data frame and choose Properties units of your data. ⇒ Click the Coordinate System tab ⇒ Click Modify ⇒ Adjust the coordinate system properties as appropriate. ⇒ Click OK Congratulations... This concludes the tutorial.
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