5 replies to this topic

[frax]

Hi,

When working with continuous raster data (like elevation, precipitation, temperature) and the display in ArcGIS, I want to play with having a smooth color ramp. Is there anyone one can, in Arc, set specific values to colors, and ramp in-between. I now that one can classify the data (using loads of classes provides a somewhat similar effect) and add a color ramp ("stretched") - but if one wants to have some degree of control over what value gets which color... ?

I am comparing with GlobalMapper where this is an easy task, one specifies colors for certain value stops, and it blends it between those...

[Crischan]

I have tried this too, and have failed. I am pretty sure there's no way to achieve that in Arc. Maybe in version 10 then...?

[oyrii]

You can define your own color ramps in styles. go to tools/styles/style manager. at the left panel select your own style set/Color Ramps.
on the right panel right click on the white space and select new/algorithmic color ramp. there you can play with colors and other options. when you finish type the name for color ramp (or not, name doesn't maters). close styles manage and you should be able to pick up your color ramp between others in symbology options.

ozren

[DaveB]

In 10.0 a new option has been added to the raster symbology dialog:
Open the raster layer's Layer Properties sheet and go to the Symbology tab
On the left, under Show, make sure it's set to use the Stretched renderer
On the right, where it has the 3 "classes", with High and Low next to the high and low values click the Labeling button
This will open a dialog titled Advanced Labeling
Set the number of intervals (this is not the number of classes, but the number of breaks between classes; so 2 intervals means you get 3 "classes")
Then click the Generate button
You can edit the color by double-clicking the color patch, or click on the value to change the break point
Once you have it set the way you want OK out of the dialogs to apply the changes
You'll see the new breaks labeled in the TOC and in the legend on the layout

[Kathi]

Hi,

When working with continuous raster data (like elevation, precipitation, temperature) and the display in ArcGIS, I want to play with having a smooth color ramp. Is there anyone one can, in Arc, set specific values to colors, and ramp in-between. I now that one can classify the data (using loads of classes provides a somewhat similar effect) and add a color ramp ("stretched") - but if one wants to have some degree of control over what value gets which color... ?

I am comparing with GlobalMapper where this is an easy task, one specifies colors for certain value stops, and it blends it between those...

You could probably achieve a semi-controlled colour ramp in ArGIS 9.x by constructing a multi-part colour ramp as ozren described, using some several intermediate steps to stretch parts of the colour ramp.

Let's say you have data where you want the lower 75 percent of the values to display in yellow colours and only the highest 25 % in orange to red. Then you'd need a four-part multicolour ramp where the first three parts go from a very light yellow to progressively darker yellows, and the last part goes from a dark yellow to red.

Obviously you will have to redefine your colour ramp when you want to achieve the same effect with a break at 60%, so this workaround is rather clumsy and may not be what you are looking for.

[Unit Seven]

In 10.0 a new option has been added to the raster symbology dialog:
Open the raster layer's Layer Properties sheet and go to the Symbology tab
On the left, under Show, make sure it's set to use the Stretched renderer
On the right, where it has the 3 "classes", with High and Low next to the high and low values click the Labeling button
This will open a dialog titled Advanced Labeling
Set the number of intervals (this is not the number of classes, but the number of breaks between classes; so 2 intervals means you get 3 "classes")
Then click the Generate button
You can edit the color by double-clicking the color patch, or click on the value to change the break point
Once you have it set the way you want OK out of the dialogs to apply the changes
You'll see the new breaks labeled in the TOC and in the legend on the layout

Thanks Dave.

I tried to do this for an atlas the other day and realised there were ways it could be achieved it was all a bit too hard in 9.3. Seemed easier to define in the old ArcInfo workstation.

v10 has just showed up here I believe (why not 2 weeks ago when I needed this?!) so am def looking forward to giving this a go!