The following data sources you added are missing spatial reference information......

[GeospatialTechnology]

Okay so i've been opening some 1km x 1km aerial photographs in ArcMap. They are in .tif format

When i open them I get the following message:

"The following data sources you added are missing spatial reference information. This data
data can be be drawn in ArcMap but cannot be projected".

How do I spatially reference the files?

I dont undestand this as they open in the correct location after the message has been displayed.

[GayathriAlallasundaram]

Hi,

That means that ArcGIS doesn't know what the projection is. It projects it on the fly if the extents are correct. First, check the data's source, a dataset will have a text/metadata file that lists what coordinate system needs to be used. If you do not know what projection it needs to be in, then refer to these KB Articles for help.

http://support.esri.com/en/knowledgebase/techarticles/detail/29129

http://support.esri.com/en/knowledgebase/techarticles/detail/29280

http://support.esri.com/en/knowledgebase/techarticles/detail/24893

-Gayu

[GeospatialTechnology]

Hello Gayu, Thanks I know that the datatsets needs to be in British National Grid and they do indeed project correctly.

When I go into "Layer Properties" and then look at "Source" the Spatial Reference is set as undefined.

How do i go about defining the spatial reference? Thanks for your help! 🙂

[TimothyHales · Accepted solution]

There are two way to define a projection for your raster dataset.

1. From the Catalog window, open the properties of the raster dataset.  Scroll down to the spatial reference information.  Click the Edit button, and then select the coordinate system.

2. The Define Projection tool will allow you to set the coordinate system.

[GeospatialTechnology]

Thanks Thales that does the trick!