ETOPO1 colormap problem

[HannuLammi]

Hi,

I'm trying to visualize ETOPO1 data by following instructions from http://blogs.esri.com/esri/arcgis/2011/09/21/using-etopo1-data/ and http://blogs.esri.com/esri/arcgis/2011/09/27/symbolizing-etopo1-data/. I've tried this a couple of times but I'm running into trouble - I'm not getting the raster file in correct format.

Following instructions from "Using ETOPO1 data" I converted etopo1_bed_g_f4.flt using "Float to raster" and saving the raster to default geodatabase. According to instructions "This step will also convert the data to the right format to be used with a color map file". However, this process created a 32-bit floating point FGDBR raster which is NOT the right format to be used with a color map file.

I still tried to follow instructions from "Symbolizing ETOPO1 data", hoping that some later step corrects the raster file. Using the "Plus tool" to make all values positive creates new 32-bit floating point FGDBR raster. Still following instructions, the next step computes unique values, but the Layer Properties -> Symbology -> Unique Values -> Colormap menu is grayed out. No wonder, if my raster doesn't have the right data type.

I'd like to know if there's something missing from the instructions or if they're not compatible with ArcMap 10.0 SP4 or if I'm doing something wrong. Is there an option somewhere which affects the results? Or should I manually convert the 32-bit floating point raster to 16-bit integer raster but the instructions have left this step out?

[MarcinGasior]

I had the same issue. But when I converted the raster to integer type (Spatial Analyst Tools -> Math -> Int), the colormap buton was enabled and I could import a colormap.

[HannuLammi]

Yes, if I manually convert the raster to integer data type, then colormap is enabled. (Although it looks like the colormap given in the "Symbolizing ETOPO1 data" needs a little tuning since by default all the continents are mostly light blue).

[PaulWalsh1]

I finally figured out that it's the ESRI "etopo1.clr" colour map that is wrong.  I opened it in a text editor and the values are all positive.  They were in the one I just downloaded from here anyways: Esri Mapping Centre - ArcGIS Resources.

So as I saw someone suggest, I edited the .clr file in Excel and subtracted every value by 10898 so that the lowest value was -10898.  However, even after doing that, the colours still didn't come out properly after I applied the colour map.  Looking at the colour map again, the light blue colour (229 255 255) stopped at 1101m where it turned into the dark green (66 209 127).  This is why a majority of the continents were still showing as light blue and only a small part was showing as green.  So I then subtracted another 1102 from all of the values and removed the values below -10898 and added values to the high end to capture all of the high elevations.

I have edited and attached the .clr files so that they start displaying green at 0m elevation and above if anyone wants to download them.  "etopo1_new.clr" is the colour map that contains the negative values and "etopo1_pos_new.clr" is the colour map with only positive values.

Also, for people having issues where the colour map button is greyed out, do the above and convert the raster to integer data type or use the Copy Raster (Data Management) tool and convert to a 16_BIT_SIGNED pixel type.  Alternatively, you can also just run the "Add Colormap (Data Management)" tool to apply the colour map to a 32 bit raster.

[JohnSchneider]

Thank you Paul!  You saved me a lot of heart ache.

I found the easiest way to load the color map was to utilize the 'Int' (Spatial Analyst) tool.

[edwardholt]

Hello,

I have been trying to visualise ETOPO1 data as outlined above, and have made good use of the Colormap files supplied by Paul (thank you). 

Because the colormap relies on unique values - it appears in the legend as some ~20,000 items. Is it at all possible to convert this colormap into a color ramp to simplify its appearance in the legend?

Any suggestions welcome.

Thanks,