Measurement tool is inaccurate
I've got a data for the Houston MSA and I'm overlaying it with ESRI's world imagery. No matter what projection I put my MXD dataframe in, my measurements are off by 16%. How can I get better accuracy with the measurement tool?
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ESRI's World Imagery map is in the Web Mercator projection, which cannot be used for measurements under any circumstances. Since this is a cached base map, its projection will override the projection of your dynamic data when you add it to a site.
To fix this, you'll need to set a valid local measurement projection in your Viewer configuration. See this Knowledge Base article:
http://support.geocortex.com/map-measurements-are-incorrect
State Plane or other similar local projections can be safely used for measurements of both length and area.
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Well that is a pretty simple solution, but I'm not finding that it works. After making the change, my measurements are still off by the same amount. In fact, I'm finding that changing the WKID doesn't even stick. When i open the site again, the WKID and the units are blank. I can change the viewer.xml, but only the wkid seems to stick if i do it that way. the units aren't sticking. I'm using silverlight viewer 1.6 and WKID 2278.
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Forcing the change in the XML seems to work, but because the units don't save in the rest manager, if I use the rest manager for another change and save, it will clear out the units and then the measurement doesn't work (and measurements are off by a factor of 10).
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Hi Ethan
have you tried making the change in viewer.defaults.xml as per the instructions here https://support.geocortex.com/how-to-edit-your-viewerdefaultsxml ?
Regards
Ralph
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I haven't tried chaning that file, primarily because I've got several apps, that have several different projections to use (different regions).
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Just to see if it works, i tried changing the measurement units in the viewer.defaults.xml file and the rest manager still didn't load the value in the rest manager and saving the site cleared the value out and caused measurements to be incorrect.
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These settings should _not_ be cleared out by saving, nor should you be required to make these edits in the Viewer.Defaults.xml. If this is happening, something else unrelated to measuring has gone wrong.
It sounds quite a bit like you are experiencing the issues detailed in this post:
Please see if the fix detailed in the thread above resolves the issue of saving these settings properly. Once they are saved you should begin to get correct measurements.
You could also troubleshoot Essentials file permissions if the above doesn't seem to be the solution. This can also prevent the correct saving of configuration files:
https://support.geocortex.com/file-permissions-for-geocortex-essentials-rest-elements
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Yes changing the web.config fixed the problem. Now the rest manager is loading the XML properly and saving the change. Thank you.
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Grrr. I don't know what happened but now my changes in the rest manager are no longer being saved. I confirmed my web.config is set to "BypassCache". Additionally, the measurement tool is off by quite a bit.
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Hi Ethan,
REST Manager works under the assumption that you have only ever used REST Manager to manage your sites. So, you must be very careful about making manual edits to the Site or Viewer configuration files. If you're using an ExternalUri to load settings from another viewer configuration, please leave the existing ExternalUri that REST manager inserts (that references the viewer.defaults.xml shipped with the management pack)
One quirk that the REST Manager introduces is that you must match the Site ID and the folder name with your sites. So, if your site ID in the Site.xml is "Charlotte", the Site.xml file must exist in a folder called Charlotte for REST Manager to be able to manage it properly.
A further issue arises if you copy a site with REST Manager and it has a viewer. The copied site will contain a viewer with the same Viewer ID as the source site, and that is also not allowed. You must either remove the viewer and re-add it, or manually change the Site.xml to fix up the viewer links so that REST Manager loads the correct one.
Another quirk with the Silverlight management pack is that the "Override Units" value on the Tool Behavior panel will do just that - override the map projection's units! This is not what people normally want to do, it's intended for users who have a viewer that is unable to determine the native units of the main map's projection. So if you have set a value in this box I suggest clearing it. The measurement tools will use the "Projection WKID" and "Projection Units" specified on the Tool Behavior panel to convert map coordinates into a suitable projection for measurement. UTM is generally a good choice for local measurement - for Arizona, WKID (http://spatialreference.org/ref/epsg/26912/) 26912 (UTM NAD83 Zone 12 North) should be a good choice.
Regards,
-Malcolm
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