topic Re: Maps in Two Projections in ArcGIS API for Flex Questions

Maps in Two Projections

BradOleson — Wed, 02 Jun 2010 18:26:39 GMT

I have a need to view my maps in the Flex Viewer (or are we calling it Flash Viewer now?) in UTM 11N. I need the data from the MGRS to be correct and that is projected to UTM. Printed maps will be used to navigate using the MGRS. However, the basemap (ESRI StreetMap, etc) is the WGS 84 projection. How would this best / most easily be handled?

Thanks in advance...

Brad

Re: Maps in Two Projections

ZahidChaudhry — Thu, 03 Jun 2010 09:34:20 GMT

I have a need to view my maps in the Flex Viewer (or are we calling it Flash Viewer now?) in UTM 11N. I need the data from the MGRS to be correct and that is projected to UTM. Printed maps will be used to navigate using the MGRS. However, the basemap (ESRI StreetMap, etc) is the WGS 84 projection. How would this best / most easily be handled?

Thanks in advance...

Brad

All the new services from ESRI are in web mercator. WGS 84 will phase out in near future.
Easiest way is to use your own base maps and then you do not need to worry about projection issues.
Although, if you want to use ESRI's base maps, you can use your dynamic map layers and server will reproject them on fly to web mercator and you will be fine but you can not do this if your map services are cached.
Bottom line is as long as your data is dynamic, it is not an issue and it will display

Re: Maps in Two Projections

RobertScheitlin__GISP — Thu, 03 Jun 2010 11:20:45 GMT

Brad,

Zahid is correct, it is best just to have your own basemaps when working with your own specific projection. One thing to add to what Zahid said though is you can use ESRI base maps in WGS 1984 that are cached as long as you add them as dynamic map services and not tiled. If you add a cached map service as a dynamic map service then the cache is ignored and ArcGIS Server will reproject on the fly. That being said you have to either specify the Extent with the UTM Spatial Reference or ensure you add your UTM map service as the first layer. The preformance of this app would be hindered though as ArcGIS Server will have to reproject evry map call.

Re: Maps in Two Projections

BradOleson — Thu, 03 Jun 2010 17:52:21 GMT

Ok, let's expound on that a little, then:

In my config file I now have moved the StreetMap layer into the livemaps portion of config.xml:
<mapservice label="Street Map" type="dynamic" visible="true" alpha="1" icon="com/esri/solutions/flexviewer/assets/images/icons/i_highway.png">http://server.arcgisonline.com/ArcGIS/rest/services/ESRI_StreetMap_World_2D/MapServer</mapservice>
<mapservice label="NVNG Imagery" type="dynamic" visible="true" alpha="1">http://ngnv-jhqj6-a014/ArcGIS/rest/services/NVNG_Site_Imagery/ImageServer</mapservice>
<mapservice label="NVNG Facilities" type="dynamic" visible="true" alpha="1">http://ngnv-jhqj6-a014/ArcGIS/rest/services/NVNG_Web_Mapping/MapServer</mapservice>

This results in listing the services in this order in the layers widget:
NVNG Facilities
NVNG Imagery
Street Map

My first question is why the order gets reversed between the config file and the widget. The second question is: does this mean the UTM layer (NVNG Facilities) is loaded first and the projection should thus be in UTM in Flex? If so, it doesn't seem so, since my UTM Grid is not "square" on the screen. Please shine a little more light on this for me? Thanks!

Brad

Re: Maps in Two Projections

RobertScheitlin__GISP — Thu, 03 Jun 2010 18:13:57 GMT

Brad,

What does the initialExtent and fullExtent in your config file look like?

Re: Maps in Two Projections

BradOleson — Thu, 03 Jun 2010 18:16:35 GMT

Here it is:

<map initialExtent="-120.2 34.6 -113.8 42.2" fullExtent="-150 -50 150 50">

Re: Maps in Two Projections

RobertScheitlin__GISP — Thu, 03 Jun 2010 18:32:44 GMT

Brad,

Those are WGS84 coordinates... If you want your map to be in UTM then you have to tell it that by setting the extent in UTM and making sure that the first map service loaded is UTM.

Re: Maps in Two Projections

BradOleson — Thu, 03 Jun 2010 18:38:31 GMT

Gotcha. I will change them. But which is the "first service loaded", per my previous reply?

Re: Maps in Two Projections

RobertScheitlin__GISP — Thu, 03 Jun 2010 18:44:42 GMT

Brad,

Based on the order of your previous post the Map would get a SR of the Street map (WGS84) because that is the first one listed in the config.xml.

Re: Maps in Two Projections

BradOleson — Thu, 03 Jun 2010 18:46:41 GMT

Ok...so riddle me this: why does the widget show them in reverse order from how they are loaded in the config.xml?

Re: Maps in Two Projections

RobertScheitlin__GISP — Thu, 03 Jun 2010 18:54:38 GMT

Brad,

Seems weird doesn't it... But the first is the last... When the MapManager starts adding the mapservices from the config.xml the first one listed is added to the map and sets the spatial reference of the map and then the next one gets added (on top of that one) and so on. So the LiveMapsWidget is showing it as one would visually expect to see it with the first layer at the bottom.

Re: Maps in Two Projections

BradOleson — Thu, 03 Jun 2010 18:57:55 GMT

Hmmm...ok...kinda one of those "why is the sky blue? Because it is..." answers, but I can live with it for now. It probably can be reversed in the widget somehow. Thanks, for sure, Robert!

I'm going to post a print question next...maybe you can chime in on. And I'm still trying to solve my ID widget issue. 😐

Brad

Re: Maps in Two Projections

BradOleson — Thu, 03 Jun 2010 21:07:17 GMT

Ok, I set my extents to:
<map initialExtent="-160300 4684100 1165200 3843700" fullExtent="-304741 6062980 4501420 3011000">
in config.xml. When the map starts, it goes to an area that there is obviously no data - just a dark screen. If I click on my old bookmarks, then the overview map zooms to the correct OLD area (in Lat/Lon), the overview map then shows map parts, and when zoomed out enough, the map shows data from the StreetMap layer, but not mine. So, something here is still not correct.

Is it something to do with the wrong extents? If so, what would make it right? And further, what needs to be done to have the overview map show the correct extents too, when things work the way they are supposed to?

Still workin...

Brad

Re: Maps in Two Projections

RobertScheitlin__GISP — Sun, 12 Dec 2021 00:49:45 GMT

Brad,

So the best way to get the values for your initial and full extent is to go to your REST Services Directory Page at http://ngnv-jhqj6-a014/ArcGIS/rest/services and choose the map service that has your most preferred data extent and there you will see values listed for initial and full extent. The overview widget needs to be set to use one of your map services that is in UTM in it's OverviewMapWidget.xml file. The second option is to add the extent and spatial reference to the OverviewMapWidget.mxml manually as in this example

  <esri:Map id="map" units="{Units.FEET}">
   <esri:extent>
    <esri:Extent xmin="661140" ymin="-1420246" xmax="3015668" ymax="1594451">
     <esri:SpatialReference wkid="26777"/> <!-- NAD_1927_StatePlane_Kansas_North_FIPS_1501 -->
    </esri:Extent>
   </esri:extent>
   <esri:ArcGISDynamicMapServiceLayer url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Demographics/ESRI_Census_USA/MapServer"/>
   <esri:ArcGISDynamicMapServiceLayer url="http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/Petroleum/KGS_OilGasFields_Kansas/MapServer"/>
  </esri:Map>

Re: Maps in Two Projections

BradOleson — Fri, 04 Jun 2010 15:26:19 GMT

Thanks Robert...that helped some.

I adjusted my extents per the rest service file. Then I commented out all map services except the facilities layer that has the MGRS grid. Everything is correct and in the right projection.

When I add back in the Street Map layer (ESRI live maps) and reload the map, the Street Map layer loads over the facilities layer. The Street Map layer is blank, but when turned off my layer is still in the correct place. To me this means the Street Map layer is not reprojecting to be where my data is. I have the Street Map layer loading with the Live Maps, rather than the Basemaps. Thoughts about what might be wrong?

I've attached my config.xml file.