For a map of UTM zones, search the Web for UTM zone map. It will be useful for you to first identify what UTM zone your data should be in. One by one, expand the folders, click a UTM projection file, then click Apply as discussed above to identify a State Plane projection.If the data does not line up after testing the State Plane options, perform the same steps above using the UTM PRJ files. Repeat, assigning different State Plane zones until the usstpln83.shp file snaps into place and the data with the unknown coordinate system appears in the correct place within the proper state. For example, use NAD_1927_To_NAD_1983_NADCON to go between NAD 1927 and NAD 1983 in the lower 48 states, and use the applicable state or regional file for transforming to High Accuracy Reference Network (HARN). Verify that the appropriate transformation method was applied in the Using drop-down menu.Click the Transformations button on the Coordinate System tab.You can set a transformation from this dialog box, or you can also examine the transformation information: A geographic (datum) transformation can reduce the offsets. This may cause offsets from a few meters to several hundred meters. The Geographic Coordinate Systems warning box may appear to warn you that the layer's geographic coordinate system is not the same as the data frame's geographic coordinate system. One by one, expand the folders, click a State Plane projection file, then click Apply.In the Select a coordinate system section, expand Predefined > Projected Coordinate Systems > State Plane.In the table of contents, right-click Layers > Properties, then click the Coordinate System tab.Navigate to the Reference Systems folder and add the file usstpln83.shp. If the coordinates, which are shown in the Extent box, are in decimal degrees, such as between longitude -180 and +180 and latitude -90 and +90, you need to identify the geographic coordinate system (datum) used for the data (such as North American Datum (NAD) 1927 or NAD 1983).Right-click the layer name in the table of contents, click Properties to open the Layer Properties dialog box, select the Source tab, then examine the extent of the data.For shapefiles, it must not have a PRJ file. The data must not have a defined coordinate system. Start ArcMap with a new empty map and add the data with the unknown coordinate system.If you set the data frame's coordinate system and the data with a known coordinate system lines up with the unknown data, the data frame's coordinate system is that of the unknown data's. If you change the data frame's coordinate system, all layers that have coordinate systems will be projected on the fly to the new coordinate system. If data does not have a defined coordinate system, ArcMap cannot project it on the fly. If a data source has a defined coordinate system, ArcMap can project it on the fly to a different coordinate system. The term projection, or PRJ, is an older term that is also used, but it is not as precise. The term coordinate system can refer to data expressed in decimal degrees, or a projected coordinate system expressed in meters or feet. This data can be drawn in ArcMap, but cannot be projected. If the coordinate system is unknown, you will receive this warning message when trying to add the layer to ArcMap: The following data sources you added are missing spatial reference information. The technique described below helps identify the correct coordinate system. Coordinate system information is usually obtained from the data source, but not always, as with legacy data.
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