Sorry for the lengthy post but felt Some background was needed: We are working with the ArcGIS- Microstation Image Server Client and are having issues when trying to add a custom coordinate system (.PRJ file) from within Microstation using the client. We wrote a program that will create a custom projection file that has a surface adjustment factor (project specific) applied to it. The Microstation Image Server client has the ability to select a projection to adjust the incoming image service. The user will select this custom coordinate system and the image service will adjust itself to match the Microstation design plane. The program takes a standard Texas State Plane PRJ, in one of the five zones, and modifies the false northing, false easting, and adds a scale factor tag based on the surface factor used in Microstation for that particular design project. We save that modified PRJ, then while in Microstation, the user selects this PRJ and the Image Server service is projected to the new coordinate system, which then matches with the design plane in Microstation (in and ideal world).
Our issue: When we simply publish the "Image Service" in Arc using any coordinate system... UTM Zone ##, TX State Plane Zone ####, GCS... then add the image service into Microstation using the Arc Image Server Client and then apply the adjusted coordinate system (.PRJ) from our program, the Image Service appears about +/- 5 feet off. However, when we publish the image Service using the corrected coordinate system (projecting from the orginal to the adsjusted CS) the imagery lines up perfectly with our Microstation design data.
Any thoughts on why this 5’ shift is happening in Microstation?
Note: We are working with the same adjusted .prj file in both instances, just getting different results. And a link to describe Surface Adjustment Factor
You may ask... why not publish the services using the corrected CS with the surface adjustment factor applied? The answer to that is; Texas is a big state. It is not feasible for us to create an Image Service for every design project in the state. Nobody has that much hard drive space. Our goal is to minimize the number of services but maximize the usage of imagery on hand.
Hey Shawn,
This may be a stupid question, but how are you able to tell your data is off +/- 5'? I am no Microstation expert so how are you creating your custom CRS in there? Are you stuck with StatePlane or could you use something like UTM?
Adam Estrada - The GIS Forum
Adam,
We are doing our testing using mapping files from our Photogrammetry Department. So, we have very percise and accurate CAD files of "on the ground" features (curbs, signs, building footprints, existing roadways, etc...) that are based on 0.25' areial imagery flown at low elevations. When we drop our services in, its easily recognizable at large scales that the services are either off or on. Microstaion does not project on the fly like Arc, its more of - it is or isn't type of precesion. I know just enough about Microstation to kick it in the shin, so I'm no expert either, but it does not use Coordinate Systems per se, its precision comes from a known distance from origin (northing, easting). To complicate things and to answer your second question - YES, we have to use State Plane because of the unique surface adjustment factors of each of our design projects. To answer your first question, we create the custom .prj through a simple program where we select one of the 5 TX State Plane Zones and multiply the northing and easting by a know Surface Adjustment Factor (something similar to 1.00011) that number is different for each project. We then apply the CRS throught the Microstation ArcGIS Image Server Client. Make sense?
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