Spatial References and also ArcGIS

Incorrect and Undefined Spatial referrals in ArcGIS

Having absent or untrue spatial references can cause significant problems for evaluation and cartography. ArcMap includes a feature called "Project ~ above the fly" whereby it will shot to project data sets to the very same spatial reference. This sounds good but create a whole collection of various other issues. If all the data sets loaded right into ArcMap have the correct spatial reference, whatever is fine. However, if one has a missing or not correct spatial reference, ArcMap will certainly still display screen the data, simply in the not correct place.

Let"s take the adhering to examples, I"ve bring away a boundary record for tacoemojishirt.com county that remained in UTM region 10 phibìc WGS 84. For one file, I removed the spatial referral (just delete the PRJ file) and for an additional I"ve changed the spatial reference to geographical WGS 84. Clock what happens once we load each of these into an empty data frame (i.e. Choose "File -> New" prior to loading every one) in ArcMap. Especially note the coordinate value and units in the reduced right.

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Figure 1. tacoemojishirt.com County effectively referenced together UTM

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Figure 2. tacoemojishirt.com ar in UTM ar 10 North, WGS 84 however without a spatial reference. In this case, ArcMap will have actually popped up a dialog letting you recognize the data set had one "Unknown Spatial Reference" and down at the bottom girlfriend may notice that the units space "Unknown Units".

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Figure 3. tacoemojishirt.com County through an incorrect spatial reference. Note that the coordinate worth is substantial (because that is actually a UTM coordinate) and also the units indicate "Decimal Degrees". Additionally note that ns did not get an error loading this data.

This shows that the is an extremely easy to have actually a absent or incorrect spatial reference and also ArcMap will never recognize the - you have actually to!

Now, let"s load all the data sets right into ArcMap together at the very same time. Then, click on the tiny earth button to zoom to check out all the data sets. You might have currently seen a window like this and also you more than likely will in the near future. Over there is a tiny tacoemojishirt.com County in ~ the top and also there is in reality one that is so small it is invisible in ~ the bottom. ArcMap is law it"s best to screen all three data set by "projecting ~ above the fly" to put them all right into the very same spatial reference. As soon as this happens, recognize that you have a spatial recommendation problem and also stop and also fix it! If you proceed, your outcomes will probably be wrong and also you will definitely be irritable working v the data.

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Fixing the Spatial References

The key to fixing all spatial reference troubles is learning when to "define", once to "project", and when to litter away the data. The flow chart below is an essential to being successful with this process.

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To inspect if the spatial referral is defined:

ArcGIS Pro: Vector and Raster Data In the "Properties" dialog for the layer, pick the "Source" tab and look for "Spatial Reference" ArcMap: Vector Data In the "Properties" dialog because that the layer, pick the "Source" tab and also look because that "Coordinate System" Raster Data In the "Properties" dialog for the layer, select the "Source" tab and also look for "Spatial Reference" BlueSpray: In the "Settings" dialog because that the layer, pick the "Spatial Reference" tab

To "define" the spatial reference as soon as it is undefined:

ArcGIS Pro: analysis Tab -> Tools, find for "Define Projection" ArcMap: Raster and also Vector Data In the "ArcToolbox" dialog, choose "Data monitoring -> Projections and Transformations -> define Projection" BlueSpray: Right click on the Scene and select "Define SR" indigenous the "Transforms" menu. If the data set is invited it"s SR will certainly be identified to match, otherwise, simply load the data set and it will certainly be characterized to match.

To fix an untrue spatial reference:

ArcGIS Pro: Raster and also Vector Data analysis Tab -> Tools, find for "Define Projection" This is the same step as above but you will get a warning in this case. ArcMap: Raster and also Vector Data In the "ArcToolbox" dialog, pick "Data management -> Projections and Transformations -> define Projection" This is the very same step as over but you will obtain a warning in this case. BlueSpray: Right click the Scene and also select "Define SR" from the "Transforms" menu. This is the same step as above but you will get a warning in this case.

To project after all the spatial referrals are properly defined:

ArcGIS Pro: Vector Data analysis Tab -> Tools, search for "Project" Raster Data evaluation Tab -> Tools, find for "Project Raster" ArcMap: Vector Data In the "ArcToolbox" dialog, pick "Data monitoring -> Projections and Transformations -> Raster -> job Raster" Raster Data In the "ArcToolbox" dialog, pick "Data management -> Projections and Transformations -> Project" BlueSpray: Right click on the Scene through the data collection loaded and select "Project..." native the "Transforms" menu. Note that you will need to have a spatial reference defined for this to be available.

Note that the "Geographic Transformation" is only needed if there is a datum shift.