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Thread: MapTips Does Not Work on GPI Prediction Layer

  1. #1
    Thomas Muench
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    Question MapTips Does Not Work on GPI Prediction Layer

    As opposed to many of the other queries in this forum, I am trying to carry out the task below directly in ArcMap and not embedded in any program code.

    The Help system (Extentions/Geostatistical Analyst/Visualizing and Managing Geostatistical Layers/Predicting Values for Specific Lacations) says that MapTips works for Geostatistical Layers and would give the predicted value at any arbitrary location on the map using the GPI generated polynomial. There is even a box to check in its Properties/Display dialogue window. However, MapTips doesn't work.

    There is a mention on the MapTips help page that MapTips might not work if there is no spatial index. Therefore, I have tried to figure out how to get ArcMap to produce a spatial index for the geostatistical layer. All the instructions I could find required the layer to be in a database of some sort. I do not use databases because it would entail major overhead and probably too complicated to arrange for all my students to learn and access it. I simply use files, although not a "file database".

    Is the lack of a "spatial index" likely to be my problem? If so, is there a way to set it up without the overhead of creating and managing a "database"?

    Maptips does work for "regular" layers (for points, lines, and polygons). It just doesn't work for the GPI created Geostatistical Layer which is not any of those three "regular" type layers.
    Last edited by tmuench; 03-12-2012 at 06:02 AM.

  2. #2
    Eric Krause

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    Default Re: MapTips Does Not Work on GPI Prediction Layer

    I'm sorry, but I can't reproduce your error. Map Tips show the value of the GPI geostatistical layer when I hover over the map.

    Please contact support services. They should be able to help you resolve this issue.

    https://service.esri.com/index.cfm?f...er_serviceform
    Eric Krause
    Geostatistical Analyst Product Engineer

  3. #3
    Thomas Muench
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    Question Re: MapTips Does Not Work on GPI Prediction Layer

    Well, the Maptips are now working. What seems to have been stopping them is apparent inconsistency in extent definitions. By clicking various settings by trial and error, I got the "visible extent" and the "full extent" to match. Then I got the Maptips. I still cannot make complete sense of the Help and the explanation phrases with the choices concerning setting the extents on the GPI layer. What really seems most strange, though, and what I don't understand, is that these "mismatched" extents seem to have no effect on the contour lines (whether filled or not). These contour lines are an obvious match for the actual tract data in gradual color and don't change when I change the "extents". I don't even understand yet how the "extents" got "mismatched". Does anybody have an idea why this great difference in behavior occurs?

    Eric, I would assume that you could reproduce my effect by manipulating the extents so they do not match. I need to better understand the setting and use of extents.
    Last edited by tmuench; 03-12-2012 at 09:59 PM.

  4. #4
    Eric Krause

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    Default Re: MapTips Does Not Work on GPI Prediction Layer

    Even after changing the extent of the GPI layer, Map Tips still works for me. Are you using ArcGIS 10?

    The default extent of any geostatistical layer is the rectangular extent of the input points. However, you should think of a geostatistical layer as a function, rather than a final result. It doesn't "know" its own values like a raster does. To find the value at some (x,y) location, the layer has to calculate the result, whereas a raster has a saved value for each cell. The geostatistical layer draws rough contour lines by making the fewest predictions it can to draw roughly accurate contours (this is why the surface often looks different after exporting to raster... this conversion simply entails making a prediction at the center of each raster cell).

    Since the geostatistical layer is essentially a function that takes an (x,y) location and returns a predicted value, you can change the range of the (x,y) locations that it will accept. ie, you can change the visible extent of the layer. Changing the range of the x and y coordinates won't change the predicted value at any locations, so that is why the contour lines do not change when you change the extent.

    Also, since the geostatistical layer does not have to store all of its values (instead, it stores a function of x,y), it essentially has infinite resolution (up to the precision of your computer); you can keep zooming in, and you will never see pixels like you will with rasters.
    Eric Krause
    Geostatistical Analyst Product Engineer

  5. #5
    Thomas Muench
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    Question Re: MapTips Does Not Work on GPI Prediction Layer

    I can now produce repeatable, predictable results controlling where MapTips works. If I set the Visible Extent to a custom rectangle, say over some of the blank space in the data view, then MapTips works only there. This is possible since the polynomial is essentially defined everywhere. Apparently, when I first set up the GPI layer, this visible extent somehow got defined over some area with no overlap with the actual map. If this happens again, at least I'll know how to fix it.

    But then I am perplexed about what the "Full Extent" box does at the bottom of the Extent tab. No matter what radio button I click ("of this layer" or "of the data frame"), when I return to this Properties tab, the "of this layer" radio button is always selected. In addition, I cannot see what affect selecting one of these buttons has. And, in addition still, the values for the "Top" and "Bottom" coordinates are reversed.

  6. #6
    Thomas Muench
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    Smile Re: MapTips Does Not Work on GPI Prediction Layer

    Well, I think I understand the Extent Tab now.

    "Visible Extent" does not refer to nor is it connected to the visible extent of the map at all, but to the extent on or around or even off the map where you want the MapTips to be visible.

    And the radio buttons and the extents that are displayed under them have no link to the "visible extent" at all. These buttons change nothing; they just provide reference information.

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