Projecting fieldwork data onto a TIFF map downloaded from DigiMap in ArcMap 10.1...

05-03-2014 02:52 AM
New Contributor
Hi, basically I have a excel/csv(table) file of northings/eastings against pH of water samples I took on fieldwork. I am trying to display the pH variation as graduated symbols on the points I sampled at along the river.

I imported the tile map of the area from DigiMap into arcmap. There was initially no coordination system for it so I went on catalog and from there selected the British National Grid coordination system for it.

I then imported the XY data, setting X=eastings and Y=Northings and Z=nothing (and selected the British National Grid as its coodination system). Exported it as a shapefile/new layer, then selected properties-symbols-graduated symbols and selected the pH data, clicked Apply and OK.

However it has failed to project the data onto the map.

Any advice ASAP (i need it done by the 6th May), would be very helpful!
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Regular Contributor III
It might be easier to georeference the tif to the points.

Not familiar with the British National Grid, but it sounds like although you may have projected the points, their values are still in their original system (GCS?).  So if your coordinates are 51.5 N 0.4 W, your point will be 51.5 meters N, 0.4 meters W of whatever the origin point is for the BNG (assuming its unit is meters). If all your points seem bunched up into a small area, this is most likely the cause. Did you define a projection as well as project the points? One quick fix that may work is to create a feature dataset in a file gdb, set its coordinate system to BNG, and import your points into that.
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New Contributor III
Can you check your dataframe properties and see if the dataframe is also BNG? Thanks

Actually reading again it sounds like the tile area from digimap isn't georeferenced. Check out the georeferencing toolbar.
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