Creating an image service for a DEM in 9.3.1 - a couple of questions...

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11-28-2011 05:49 AM
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TimothieBiggs
New Contributor II
I am working with image server for the first time and I am wondering if anyone can help shed any light on my situation:

a) I have a DEM in ESRI GRID format, including pyramids - created by a third party in ArcGIS 10.
b) I have ArcGIS Image Server 9.3.1 the standalone image server product.
c) I will be working with the DEM in ArcGIS Desktop only (currently 9.3.1 but possibly also some test copies of ArcGIS10) - the DEM will not be utilized in any web services.

Questions:
1) Do I need to reformat the DEM (or preprocess/prepare the DEM in any way) or can I go straight to the step of creating the image service definition.
2) Given that I am just utilizing the images in ArcGIS Desktop does ArcGIS Server even come in to the equation?
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PeterBecker
Esri Regular Contributor
>1) Do I need to reformat the DEM (or preprocess/prepare the DEM in any way) or can I go straight to the step of creating the image service definition.

You can directly use the grid data and add it to an Image Service Definition (ISDef). I would generally recommend converting the data to TIF (either 16bit signed or 32bit float) with LZW compression and then create pyramids. As you are using 9.3.1 directly it is better to create internal pyramids or RRDs. At 10.0 I would recommend creating pyramids OVRs (or internal). Although Grid files are supported, the performance of TIF can be better especially when serving to multiple users simultaneously. If you are primarily using Desktop, I would recommend that you keep the existing files and possibly convert later to TIF when you transition to 10.0 or 10.1 and are looking to serve the data. If you do convert the data, ensure that the data is not re-projected in the process as an type of sampling will always negatively affect the accuracy of the data.

>2) Given that I am just utilizing the images in ArcGIS Desktop does ArcGIS Server even come in to the equation?
If you are just using in Desktop then you can directly use the Image Service Definition editor that will provide quick access to collection of elevation data. To use the Image Service Definition editor requires a license of the Image Extension for ArcGIS Server, so it would make more sense to create the ISDef and then serve it as an image service.

I would strongly suggest that you look to upgrading to 10.0 (or 10.1 Beta2) and use Mosaic Datasets instead. These have replaced Image Service Definitions. Mosaic Datasets are a similar concept to ISDefs, but are more more capable, integrated and scale better. Mosaic Datasets are a a core component of ArcGIS Desktop at 10.0. They can be created with ArcGIS Desktop (Editor or Info License) and can be used with all ArcGIS Desktop application. This enables them to be used in a local or work group setting directly as well as served as image service through ArcGIS Server and the Image Extension. You will find it much easier to create mosaic datasets of a wide range of different image and rasters. There are a number of workflows the detail how best to create Mosaic Datasets and Image Services from elevation data (see http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#/Part_1_About_elevation_data/009t000002...)
Also review the World Elevation Services that are currently (as of 15th Nov 2011) in Beta. See http://www.esri.com/worldelevation. These services provide direct access to a wide range of multi-source, multi-resolution elevation data and derived products. These can be directly used in a range of applications including 9.3 desktop.
Similar Mosaic Datasets can be create using using your own data with ArcGIS 10.0 and then if required served as a range of image services.
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TimothieBiggs
New Contributor II
Thanks for replying Peter.

This will be my first time using image server. When you say its better to 'create internal pyramids' do you mean delete the ones that came with the GRIDS and create new ones as part of the process of creating the image service definition? Or do you mean create pyramids in 9.3.1. before creating the image service definition?
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PeterBecker
Esri Regular Contributor
Grids contains internal Pyramids. Leave these as they are.
If you do convert the data to TIF then create pyramids for larger files. These can be RRD files (but do not compress well), Internal overviews or at 10.0 we have defaulted to using .OVR files (these are actually a lower resolution TIF file with internal pyramids)
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