Raster Grid Legend

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03-28-2013 11:58 AM
Status: Open
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RichPriem
New Contributor III
Legend requirements are different for raster grids then feature data types.  The raster/grid legend options are weak, and need more advanced capability.  The color ramp for grid rendering needs to be displayed and labeled much better.  And for contour lines derived from grids, it is crucial to put the contour increment in the legend.
 
Note:  this request has been on the PUG List for many years, currently at http://www.pugonline.org/index.php?q=raster-legend
This is a quick summary, and I will gather and post additional information in subsequent Comments to this item.
For additional information, eMail  Rich@Priemere.com
 
6 Comments
RichPriem
Below are detailed notes that were originally posted posted in 2009 to the PUG Sharepoint Site, and subsequently lost when moved to other formats.
 
The Petroleum Industry has been making "contour maps" for a long time, and many industry specific mapping software (Zmap, etc) have established standards for comparison. ArcMap offers many improvements over these aging vertical products, but to compete must do better at creating acceptable contour maps. Customers must be able to easily view the legend and estimate the grid value at a particular location from the color bar, or estimate the change in value between two locations based upon the changes in color, or the number of contour lines crossed.

Obviously, for interactive viewing of a Map, the Identify tool is excellent for interrogating grid values. But for printed maps, or images displayed in other software (powerpoint), it is still necessary to create an acceptable legend. Here are some specific suggestions:

1. Contour Lines: there needs to be a new rendering option for contour lines. This is another list item. The renderer should be able to place multiple annotations along a line, and provide some options for the placement of the labels. And it should be able to skip labeling very short lines (bulls-eye). The renderer should know the contour increment for the lines, and provide options to display a different increment, or make every Nth value bold. Then, for the legend, the renderer must report the contour increment that is displayed. Obviously, this assumes that the contours are evenly spaced, so maybe there are two different renderers for equal and irregular spacing.

2. Raster Legend Orientation: we need the flexibility to make either horizontal or vertical color legends. The current vertical options are tolerable, but not the horizontal options. For a horizontal legend, the labels must also be horizontal, or provide an optional angle. And if there is not enough space to fit the label, there need to be intelligent options to either shrink the label, reduce the frequency of labels, or stack the labels alternating on two or more lines.

3. Raster Stretch Renderer: this renderer automatically labels the min/max grid values, and offers a third spot where the user can provide a label in the middle. This is not adequate. There should be at least 5 labels. Automatically display the Mean or Median value between the Min/Max. And add the P25/P75 values too. Better yet, make the number of labels a user option that defaults to 3 or 5, but can be set as desired, similar to the classified renderer. The labels should be evenly spaced along the color ramp, but may not be at even numerical increments, if a custom histogram is applied to the stretch.

4. Raster Classified Renderer: suggest that there be two flavors of this renderer. The current flavor labels groups between each break value, and that is good if you want to give text labels to each group. But if the group is labeled with the start/end value, that is pretty silly. In that case, the single break value should be labeled at the boundary between the adjacent colors. The labels should be rounded to "nice" values, not display a bunch of extra zeroes after the decimal point. Or maybe offer a user option for rounding or formatting. And, per above, there need to be better options for making a horizontal legend.

TO BE CONTINUED, exceeded 4000 character limit. . .


RichPriem
Continuation of previous comment.


5. Visible Extent: this option on the stretch renderer is great, so it adjusts each time you pan or zoom the display. However, the legend does not keep up with these changes. It continues to report the constant min/max from the entire raster dataset. Also, when creating images from current display, the rasterizer appears to scan the extent in swaths, which triggers a reset of the colors on each pass, making a very confusing image which is not what you see on the screen.

6. Legend Defaults: there needs to be a method to alter the default settings when new layers are added. When creating the Legend, you can select all and change the style. But when new items are added, they revert to the ESRI default, rather than the same as all of the other layers already modified. So the user has to go back and reset all of the new layers before making displays.

7. Legend Properties: there also needs to be some work in this area. First, it appears to always be anchored on the bottom left corner, and grow up and to the right when new items are added. Like many other Map Surrounds, it needs to honor the anchor points specified in the size and position properties. And sometimes we don't want it to grow, but rather have the content adjust to fill the available area: either by increasing or decreasing the size, and/or truncating some of the long trext that dangles to the right.

8. Mockup:  lost it somewhere, have to find and load again later . . .

If you begin to work on this item in earnest, I (Rich) would be glad to assist further with requirements, discussion of design, mock-ups of new legends, etc. . .
RichPriem
Below is image showing mockup of a nice grid legend.  Below for comparison are images from current ArcMap 10.1 options, both horizontal and vertial, for stretched and classified renderers.

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Notice a few key improvements in the mockup:
1. Round:  numbers are rounded to an appropriate number of significant digits, which can be determined from the range of values.
2. Breaks:  the break values are labeled between the colors, rather than duplicated as the beginning and ending of individual color labels.
3. Horizontal:  labels are horizontal, so they can be read easily.
4. Stacked: labels are stacked to accomodate extra space required.
5. Skipped: not all breaks need to be labeled.  This example shows every other labeled.
SimonWoo
by Anonymous User
Pug Idea List 2014:  Steve Kopp, ESRI Lead
From Rich: Is it possible to get help jump starting a custom solution with a new legend object and visualization to prototype and give back to Esri.  From Steve Kopp: Need a better way to handle legends across the board, need to check with the mapping team.
 
 
RobertGraham
The Raster Legends issue will be raised up to the ESRI Developers through the PUG (Petroleum Users Group).  Geoff Wade directed the workgroup to connect with Steve Kopp to better understand the issue and simplify the raster legend dialogs.