[GIS] How to adjust online basemap to Arcmap

arcgis-9.3arcgis-online-basemapsarcmapdatumimagery

How can I adjust the online basemap imagery file to our existing ArcMap data. Below are steps I perform to add the basemap data.

  1. I Added basemap from "Add Data From GIS Online" in the file menu and
    then selected Imagery and added to the Desktop.

  2. I already have some layer files in our current project in arcmap the details of our

    Qatar GCS (Datum)
    :

    Qatar Projection: Transverse_Mercator 

False_Easting: 200000.000000

False_Northing: 300000.000000

Central_Meridian: 51.216667 

Scale_Factor: 0.999990

Latitude_Of_Origin: 24.450000

Linear Unit: Meter

GCS_International_1967 

Datum: D_International_1967

    ====================================================================

and the imagery from online data GCS(Datum) :

   WGS_1984_Web_Mercator_Auxiliary_Sphere

   Projection: Mercator_Auxiliary_Sphere

   False_Easting: 0.000000

   False_Northing: 0.000000

   Central_Meridian: 0.000000

   Standard_Parallel_1: 0.000000

   Auxiliary_Sphere_Type: 0.000000

   Linear Unit: Meter

   GCS_WGS_1984

   Datum: D_WGS_1984

Now the problem is the added imagery data is looks like it's shifted around 100m difference with our arcmap hole data.

then I tried transformations to adjust with our arcmap data by selecting the same as our Datum: D_International_1967 in the dataframe properties but not changed anymore. and then i tried different transformations named as Qatar but same result not aligned the data.

am I trying to do the transformations at the right place.?? and any thing i missed here.???

  1. **Right click in the arcmap\Datafareme properties\Coordinate system tab\Layers\selecting the desired layer to transform\transormations\convert from (selecting existing GCS)\into (Selecting desired GSC)
  2. hit Ok.**

Best Answer

You are trying to view data from two datums so will need to use a Transformation.

I'm not familiar with datums used in Qatar but on the Coordinate System tab of the Properties for your data frame you should be able to find a Transformations button which should offer you choice(es) based on which datums are in the data frame.

Try these steps using ArcGIS 9.3 (I am using ArcGIS 10.1 SP1 but the steps should be basically the same):

  1. Start ArcMap with a Blank Map
  2. Use Add Data | Add Basemap to add the Imagery basemap
  3. Use the Find tool to locate and Zoom To the State of Qatar - then set the scale to 1:250000
  4. Use the Coordinate System tab of the Properties for the Basemap layer and you should see that it is WGS_1984_Web_Mercator_Auxiliary_Sphere
  5. To change the Coordinate System of the Data Frame for display (do NOT use the Layers part of the dialog) choose Predefined>Projected Coordinate Systems>National Grids>Asia>Qatar National Grid.
  6. Hit the Transformations button and chose to Convert from GCS_WGS_1984 to GCS_Qatar_1974 using Qatar_1974_To_WGS_1984_3
  7. Hit OK to accept the Transformation and OK again to display the map in the Qatar National Grid coordinate system

I don't have any data to add and observe the result but am confident that if it was in Qatar National Grid it would line up. However, depending on where in Qatar it was it might be that Qatar_1974_To_WGS_1984_1 or Qatar_1974_To_WGS_1984_2 were slightly better than my first choice above.

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