Quality issue with raster images

Question

Hi all,

I'm trying to re-build a map that was originally created by an ex-colleague of mine (said colleague left all the data sources in the map linked to files on her own laptop rather than the server).

The map uses a raster image of an Ordnance Survey 1:50k tile as a base: when I repair the link to the raster image, the resulting quality looks terrible (way worse than on the original layout). I'm not particularly experienced with ArcGIS - does anyone have any ideas as to why the quality is so poor, or tips for improving it?

TIA

JessicaSkelton · Answer

Hi, hope the following sheds some light:

1. The examples I posted used two different OS tiles, but the same effect is seen with all the 1:50k raster tiles I have access to in ArcGIS Pro. I'm definitely using the same data source that was used for the original maps.

2. I don't have ArcMap installed, and I can't find a download version. Is this called something else in version 10? (Sorry for the newbie response - all my previous GIS experience was with MapInfo.)

3. It's using a predefined colourmap of some sort. I can't tell if it's RGB - looks like 8-bit as there are 256 colours listed in the contents pane.

4. The raster is a TIFF (with LZW compression)

5. It's using Nearest Neighbour resampling. I've tried each of the options, to no particular improvement.

GabrielUpchurch1 · Answer

There is definitely a difference there, especially with the text.  A few questions:

1. To verify, this is the same raster?

2. If you add the raster to ArcMap instead of Pro, do you still observe the poor rendering?

3. Is the raster using RGB symbology (as seen in the Contents pane) or something else?

4. What is the format of the raster (e.g., tiff, sid, jpg, etc.)?  You can check this under the raster's properties if you are not sure.

5. In Pro, select the raster in the Contents pane and select the "Appearance" tab.  What "Resampling Type" is being used?

JessicaSkelton · Answer

Sure, and thanks for responding. The image below is an extract from a map that was created by one of my colleagues using (I think) ArcGIS 9. Apologies for the cut-outs, but some of the information in the original maps is commercially-sensitive (and I can't recreate the original map to hide the shapefile contents in question, which is part of the problem 
). It's the issue with the raster text that I'm most concerned with.