XY data doesn't match with raster extent

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12-27-2018 08:23 AM
caiovillaca
New Contributor

Hi everyone,

I'm facing some problems with my work and I'm looking for help.

There are mainly two problems.

First problem: I'm working with data from Pluto and the longitude of the DEM (https://astrogeology.usgs.gov/search/map/Pluto/NewHorizons/Pluto_NewHorizons_Global_DEM_300m_Jul2017) should be shown from 0º to 360º, but the data frame goes from 0º to 180º (midle of raster) and than -180º to -0º(end of raster). I would like to know if is there a way to change the longitude range to 0º to 360º?

Second problem: I'm trying to add a xy data from a csv file (https://astrogeology.usgs.gov/search/map/Pluto/Research/Craters/Craters_PlutoCharon_System_Robbins). The problem is that the xy file do not match with the DEM. The xy data should be added as decimal degree but it looks like the arcmap read coordinates as meters. The result is that all the point ploted are concentreted in a tiny little spot within the DEM. How could I make the sotware plot the xy data as decimal degrees?

Both xy data and DEM are in the same coordinate system and projection.

I'm sorry about any english mistakes or any confusing information.

Many thanks in advance.

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4 Replies
ChrisDonohue__GISP
MVP Frequent Contributor

For starters, in terms of viewing the data, can you check the Coordinate system set in the Table of Contents in ArcMap to see if it is what is expected?  (Right-click on Layers in the Table of Contents, then click on the Coordinate System tab).  The Table of Contents inherits the Coordinate System of the first layer loaded into it, so make sure it is using the one you expect.  Also, check the coordinate system of the DEM to see if that is what is expected.  It is possible one or more of the layers you are using do not have an specifically-assigned coordinate system, so are "free floating" and instead rely on the underlying Table of Contents coordinate system to align.

If coordinate system is correct in each case, there are other possibilities that come to mind:

  • For your First Problem, it may be necessary to use a custom coordinate system if the one you are currently using does not do a range of 0 to 360. 
  • For the Second Problem, the issue may be in the XY data conversion not having a correct assignment for the Coordinate System.  Be sure to specify an appropriate coordinate system when running the conversion to help avoid issues (many people forget to do this).  Adding x,y coordinate data as a layer—Help | ArcGIS Desktop 

Chris Donohue, GISP

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MelitaKennedy
Esri Notable Contributor

Try adding the attached shapefile (extract from the 7zip file) first to your map, then add the DEM. This will tell ArcMap that the geographic coordinate system is supposed to have a longitude range of 0-360. If it doesn't work, and it may not, you may have to do some adjustments like use the define projection tool to update the shapefile's coordinate system to use the DEM's. 

Melita

caiovillaca
New Contributor

Hi Melita,

Adding your .shp first solved the longitude range problem! Could you explain me what did you do? haha

Also, about my second problem, now when add the xy data with no coordinate system the data seems to plot correctly, but when I set a coordinate system I get my old problem( the xy data doesn't match the DEM), I don't know why. haha

Also, when I add you .shp, the pixel of the DEM changes its size, so my measurements become incorrect. Do you have any ideia what could be cousing this?

But any way, many thanks . I think you already helped me a lot.

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MelitaKennedy
Esri Notable Contributor

We can't get to the data due to the US government shut-down. Can you please post the extents of the DEM and the xy data--or just sample coordinates of the xy data if you can't get the full extent. What coordinate system is listed for the DEM?

Thanks,

Melita

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