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oz1

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oz1 last won the day on December 6 2012

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About oz1

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  1. oz1

    DEM DATA ALOS 5M

    Geoimage in Australia claim to supply. We haven't bought from them as yet & they say that the ALOS people are not the easy to deal with so might be worth a try. They close for Christmas soon. https://www.geoimage.com.au/-dems/5m-grid
  2. Creating DEMs from contours commonly produces steps around the contour locations unless the contours are very closely spaced. Try looking at the histogram of your DEM with small bins to see how bad the problem is. One partial solution I have used along streams is as follows: 1. Extract the points along the individual stream segments then interpolate elevations between them. For example, let's say your elevation points are 50 m apart (distance not elevation), then create a set of points 10 m apart. I believe the ET Geowizards let's you create these "station points". Hawth's Tools us
  3. Mamadouba is dead right about the need to understand the landscape & the rate of change. Also, you need to be aware of what NDVI actually measures. The following points apply: 1. NDVI or a similar index (they all have pluses & minuses) will tell you something about how green vegetation changes. It is not a good indicator of dry vegetation.Thus, after rain, you will get a strong NDVI signal but after green vegetation dries off, it becomes yellow, brown or grey & your NDVI signal drops off, even though you may have exactly the same amount of ground cover by plants. Essentiall
  4. Thanks Darksabersan. You're a gentleman.
  5. Would appreciate some help with this as the help section doesn't I have a jpeg RGB image "test.jpg" with some white areas that I want to set to null. The white values are B=251, G=255, R=255. I cannot for the life of me get ARCMAP to do this. Have been trying Set Null from the Spatial Analyst conditional toolbox as follows: Input conditional raster - test.jpg Expression - value>=251 Input false or constant raster - test.jpg Output raster - SetNull_jpg4 Result is an error message: ERROR 010152: Object IRasterStatistics is null. ERROR 010152: Object IRasterStatistics is nul
  6. Does anybody know what's going on? When I search the Glovis website, it is no longer possible to download any Level 1 imagery for Landsat 4 & 5 data. That product is greyed out in the Item basket
  7. What software do people recommend for gridding lidar data. What pros & cons for each software package. Thanks
  8. oz1

    Grid Editor

    thanks Lurker
  9. oz1

    Grid Editor

    Could anyone recommend a grid editor please. I want to modify the values in a floating point tiff file, preferably on screen There used to be a good one in TNTMIPS but I don't have it any more.
  10. Thanks for the veg index info Emperor. Looking at the size of trees suggests a resolution of 1-2 m is needed.
  11. I would like to monitor forest dieback over time using remote sensing. It's happening in scattered small areas & is very patchy so Landsat TM does not have enough resolution. Could anyone help by suggesting which satellite to use (Worldview?) and what is the best vegetation index or data transform please?
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