Problem with coordinate referencing

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11-03-2012 10:21 AM
New Contributor
Hi,

I have a shapefile and a raster that do not coincide with the same coordinate system in ArcGis 9.3

The shapefile has a undefined coordinate system in which there is pop-up window saying "The following data source you added are missing spatial reference information. This data can be drawn in ArcMap, but cannot be projected." I decided to define projection for this shapefile. After defining it, I project the shapefile to the new Geographic Coordinate System.

The raster also has a undefined coordinate sytem which had the same pop-up as the shapefile. Again, I define projection for the raster to be the same as the shapefile. Hence, the spatial reference for the raster is the same as the Geographic Coordinate System for the shapefile.

The problem is that even though I did the same method for both the raster and the shapefile (as mentioned above), they do not converge at the same location. After that I tried to use the "project raster" tool and I found that the input coordinate system (optional) is "unknown".

The first issue is why cant both the raster and the shapefile converge at the same location? The second issue is why is the input coordinate system (option) unknown? So how should I go about resolving this problem?
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Frequent Contributor
Bernard-
I've had the chance to get back to this after you sent me the data, and yes your problem is the projection is not defined in the files, so ArcMap cannot project 'on-the-fly'.  All this means is when ArcMap 'finds' or reads along with the data any projection info, then it'll do the 'transformation' in the view, thus 'on-the-fly' or dynamically - the transform won't be saved with the file(s).  If you need the files stored with the transform (not just as viewed within ArcMap) then you can use the Project tools...these only work after coord sys have been defined.

So I've defined them - read the provided articles, etc., to learn more about 'discovering' them.  What I found was this:
- the 2 shapefiles:  GCS_WGS_1984
- the grid raster:    Kertau_UTM_Zone47N

I'll zip up and send to you your data and include a 9.3-compatible mxd referencing this data (on-the-fly, coord sys defined) so at least that'll give you a head start on using this result.  I'll leave any Project operations up to you...

Enjoy!

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Frequent Contributor
This can be a common problem in dealing with data from multiple sources or agencies.  Also, I have found it to be a fairly common 'novice' mistake to encounter a dataset with missing spatial reference info, assume it's in a particular projection and incorrectly define it.  ArcMap will attempt to 're-project' on-the-fly and if you receive data with missing spatial info and consequently define it incorrectly, then of course it won't overlay properly with anything else.  If you need to use Project to bring data into your GIS's native spatial reference, it must be defined correctly 1st.

There's no way to troubleshoot your data without knowing more about it...but maybe now you understand your problem better.  It would help if you could get the spatial reference info from whereever you got your data.  At least you can troubleshoot, starting with this article online:

Learn to Identify an Unknown Spatial Reference
By Mark Romero
Esri Technical Marketing
http://www.esri.com/news/arcwatch/0111/tip.html

Hope that gets you started.  If you'd like, I could take a look if you want to attach a sample - clip a sample area if the files are too large too attach.
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New Contributor
Thank you for your comment.

I have contacted the person for the spatial info and is currently waiting for his response. In the mean time, how do I transform a Geographic Coordinate System to a projected coordinate system?
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Frequent Contributor
Once you've determined and properly defined the gcs (or projected coord system, like 'state plane' commonly used by local gov) which you can do with the Define Projection tool of Toolbox, then you can use the Project tool to run the transform automatically from what it is defined as to what target projection (or gcs) you want to go to.  For example, I commonly go from WGS84 (a gcs, lat/lon) to our state plane (projected, feet) coord sys.  See:

Project (features) ---
Project (Data Management)
Resource Center » Professional Library » Geoprocessing » Geoprocessing tool reference » Data Management toolbox » Projections and Transformations toolset » Feature toolset
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00170000007m000000

Project Raster ---
Project Raster (Data Management)
Resource Center » Professional Library » Geoprocessing » Geoprocessing tool reference » Data Management toolbox » Projections and Transformations toolset » Raster toolset
http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Project_Raster/00170000007q000000/

PS - I got your message and have sent you my email - however I would advise you attach here (or send me if you prefer) a clipped sample of your datasets.  I sent you both clip help references if you need them.
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Frequent Contributor
Bernard-
I've had the chance to get back to this after you sent me the data, and yes your problem is the projection is not defined in the files, so ArcMap cannot project 'on-the-fly'.  All this means is when ArcMap 'finds' or reads along with the data any projection info, then it'll do the 'transformation' in the view, thus 'on-the-fly' or dynamically - the transform won't be saved with the file(s).  If you need the files stored with the transform (not just as viewed within ArcMap) then you can use the Project tools...these only work after coord sys have been defined.

So I've defined them - read the provided articles, etc., to learn more about 'discovering' them.  What I found was this:
- the 2 shapefiles:  GCS_WGS_1984
- the grid raster:    Kertau_UTM_Zone47N

I'll zip up and send to you your data and include a 9.3-compatible mxd referencing this data (on-the-fly, coord sys defined) so at least that'll give you a head start on using this result.  I'll leave any Project operations up to you...

Enjoy!

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