warning, inconsistent extent!

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12-01-2019 11:30 AM
Anastasia_Ejov
New Contributor

Hello,

I am working on an analysis (coursework) using population density and crop .asc data. With either crop or popd grid loaded, I draw a rectangle around the country I am working on and convert graphics to features. 

I need to clip both crop and popd grids.

Then I define their projections as WGS84. 

Reprojecting as raster to UTM 38S WGS84. 

My problem is: When I reproject, I get an error saying 'warning, inconsistent extent'

I have no idea how to proceed. 

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10 Replies
DanPatterson_Retired
MVP Esteemed Contributor
Then I define their projections as WGS84. 

Were the data actually in the WGS84 coordinate system? 

Projecting the data if it were not in the coordinate system that you thought it was in will make the Project process faulty.

Error: Warning, inconsistent extent! 

How To: Identify the spatial reference, projection, or coordinate system of data 

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Anastasia_Ejov
New Contributor

What do you mean by ' if they were actually in the coordinate system'? 

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DanPatterson_Retired
MVP Esteemed Contributor

WGS84 is a datum, not a coordinate system.

Are the data you projected in  a GCS WGS84 coordinate system?  That is, a Geographic Coordinate System, with units of decimal degrees?

or do you have a projected coordinate system with a WGS84 datum?

Or maybe a Web Mercator (projected coordinate system) with a WGS84 datum?

Is the data extent between -180 to 180 in the east west direction and 90 to -90 in the north south direction?

Just because a dataset has a coordinate system, doesn't mean it was defined properly.

Further, if the user defines one, because there was no coordinate system in the first place... they better define it correctly.  That is the purpose of the last link.

If you don't check the extent yourself and confirm the metadata yourself, then "defining" a coordinate system can be an error prone venture.  And, if it is defined wrong, projecting it won't make any better, but undoubtedly worse.

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Anastasia_Ejov
New Contributor

Yes, we define projected the clipped crop and popd grids to Geographic WGS84 then re projected to UTM 38S WGS84. 

If the data extent is not between those numbers, how do we fix it? 

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DanPatterson_Retired
MVP Esteemed Contributor

What are the extent (left, right, top, bottom) values?

are they small numbers like I listed above? (ie, they will fit anywhere on the world described in decimal degree values)

or are they numbers > 180?

Doesn't the *.asc file have header information? (open it in a text file) or a world file?

It should provide information on the location of the top left or bottom left corner plus a cell size if the asc is a raster

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Anastasia_Ejov
New Contributor

Yes, 

xllcorner -180
yllcorner -90
cellsize 0.0833333
nodata_value -9999

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DanPatterson_Retired
MVP Esteemed Contributor

so they are in the proper extents -180, -90 being in Antarctica along the dividing line between the eastern and western hemisphere.

If you defined it as a Geographic coordinate system, THEN you need to clip it using geographic coordinates for that UTM zone 

WGS 84 / UTM zone 38S: EPSG Projection -- Spatial Reference 

or your study area in Geographic coordinates.  Once it is clipped in using a clipping polygon, you can then project it.

If you skip that step, you will get that error, because extents of your asc files are probably for the world and you can use a UTM 38S to project it PRIOR to clipping

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Anastasia_Ejov
New Contributor

We define the projection of the asc. as Geographic WGS84 then clip it and then project to raster UTM? 

I'm a little confused what you mean by geographic coordinates for the UTM zone. 

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DanPatterson_Retired
MVP Esteemed Contributor

Your utm zone is a small slice of the world.  you are clipping with some polygon.  Make sure the polygon is in decimal degrees (GSC WGS84), project it to that if it is currently in UTM coordinates

Clip the file using the decimal degree version, then project it

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