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Struggling to produce and export a correctly georeferenced image.

RobertHall1

Dear all, i'm currently struggling to produce a simple, georeferenced image to use in Arc and also export for use in other programs like 3D Move and Google Earth. What i have is a simple, scanned jpg of a fieldmap overlay that my old Phd supervisor gave me. It's ~56mg and has no other metadata stuff attached. What i need to do with it is to create a version of the image that I can open in other programs and have it locate the image correctly so that I can then add and edit data, and then export that data into a database.

My main problem is that the basemap on which the mapping was done is in NGO1948 Zone 5. I have added the jpg to a fresh project that has been configured to use the projected NGO1948 zone 5 coordinate system, and built the pyramids with no problem. I have used a number of control points around the image and given them their values as taken from the grid system on the map. However, I can't then convert the coordinate system to a system such as WGS84 or similar that Google Earth and the other programs can understand. When i change the coordinate system to WGS84 (or any other), the image is altered, but certain marker points are not in their correct locations. For example, there is a town on the map, which Google Earth locates at 17°48'19.87"E 68°44'48.59"N, whilst Arc shows the same town at roughly the same Easting but at ~58°N, so the conversion is clearly going wrong somewhere.

My second problem is that when i export the map, the GeoTiff i produce doesn't appear to have any data embedded (correct or not) to tell other programs where the image should be located. The GeoTiff is also very low quality, so that when i zoom in in GE to look at the data points on the map, the resolution is too low and the data has been lost. This is using the "export map" option in the file menu, and then saving as tiff with max JPEG quality and "write GeoTIFF tags" selected.

Many thanks for any help!

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JohnSobetzer

You can reproject a properly defined raster to a new coordinate system using the Projections and Transformations - Raster - Project Raster Tool. See the Help before using it since there are options that are relevant to some of what you have discussed and to the use of the tool generally. Specifically you may need to set a transformation to get an accurate reprojection. I just did a quick Google using "transformation between wgs84 and ngo 1948 and came up with some information that might be useful. It may be that ESRI already provides a good transformation but if not it looks like you may be able to download one.

RobertHall1

Hi Amyeallen1. I can't help you sadly, but i think you'll have more luck finding an answer if you made your own thread that everyone can see.

AmyAllen

Hi,
I'm getting an error "invalid extent for output coordinate system" when I try to project a feature class from WGS 1984 into UTM Zone 4 or Zone 5, but the feature class projects fine into UTM zones in the continental US. What might be wrong?
Thanks,
Amy

RobertHall1

I'd like to get my methodology checked if I may. So far, following the kind replies in this thread I have: Imported basemap without building pyramids, then georeferenced the image in the projected system that the original map was in, then rectified the image and created an uncompressed tif and a compressed tif (just to have options with filesize). I have then created a new project set up in WGS1984 and added the georeferenced tif as a new layer, allowing Arc to transform the image. Once I get to this point, I'm not sure what to do next, so I have right-clicked and exported the data, selecting "extent: data frame (current)" and "spatial reference: data frame (current)" but leaving the other options untouched. I'm not sure these are the options I need to use, or even if exporting the data like this is the correct way to get the image that I need from the program. Again, I have done this twice to create an uncompressed and a compressed image. Is this the correct way to go about obtaining a map that is georeferenced in WGS1984 (or any global geographical system) from a map that is using a projected system?

Secondary to this, my reference point on the map (a town in Norway called Tennevoll) is not converting to where it should be. On the projected system of NGO 1948 it sits at ~13500 29000, which should correlate to 17.8E 68.7N but actually converts to 17.1E 58.3N on the WGS1984 converted map. Is this a conversion error, is the basemap at fault, or is something else happening?

Many thanks.

RobertHall1

Dear Eric, changing the permissions of the default directory didn't work, but creating a new directory with write permissions worked a treat. Thank you very much!

EricBowman

Hi Robert,

Make sure you have read/write permissions on the output location and would make sure the format is a stand alone raster not stored in a geodatabase. If you can't rectify it, you may want to just create the world file for the jpg and then use the conversion toolbox geoprocessing tool Raster to other format to create your tiff. I had this error before and I think you will need to find a different output directory with permissions.

Hope this helps,
Eric

RobertHall1

You might start over removing all the other associated files, including the pyramid files, leaving only the raster. Start a new project. Georeference the raster in the coordinate system the map was made in. Rectify that and use that raster.

Got as far as the rectifying but still can't rectify the georeferenced raster. The error is "failed to save raster dataset" as before. I've tried all of the compression types for all of the resamplying types. I've tried it both before and after updating the georeferencing once the control points are in place and the same error each time. I'm running Arcmap 10 on a brand new install of Win7 ultimate.

JohnSobetzer

You might start over removing all the other associated files, including the pyramid files, leaving only the raster. Start a new project. Georeference the raster in the coordinate system the map was made in. Rectify that and use that raster. Then if you want build pyramids, change the coordinate system of the data frame, project it to a new coordinate system, etc.

RobertHall1

Thank you both very much for your help. When I try and rectify after adding my control points I get a "failed to save raster dataset" error no matter which options I select for the rectifying. This is why I was trying to use the export map function as it was the only one that didn't give an error.

EricBowman

Hi Robert,

Here's an ArcUser article that covers georeferencing - http://www.esri.com/news/arcuser/0102/winter2002.html Be sure to download the data and the pdf. It's called Registering Images in ArcGIS.

Hope this helps.
Eric

MichaelStead

Not sure where to start. It sounds like you have somehow figured out how to use the georeferencing tool. You should really try georeferencing the scanned image in the projection it was in, then export a copy of the raster, not the export option from the file menu. You can do this from the Georeferencing toolbar using the Rectify option or by right-clicking on the layer and exporting from the TOC. Once you have exported this you can reproject the output.

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