Difference between revisions of "Tarsier tutorial: Rendering symbols from rasters"

Revision as of 13:45, 4 December 2009

Outcomes

• Render Fort Ord in a 3d realistic virtual reality
• Use your land cover map to populate the visualization with trees and shrubs where appropriate, and at a density dictated by your % green cover map

Prerequisites

• Download and install Tarsier

Data

• Fort Ord land cover map derived from Landsat (and associated land cover metadata)
• Fort Ord % green cover derived from Landsat
• DEM (download from USGS as a *.flt file - http://seamless.usgs.gov/index.php)

1. Define download area
2. Change to *.flt format
   1. Click on Modify Data request at the top of the download box
   2. Wait until the modify data request window loads
   3. Uncheck 1 arcsec and check 1/3 arcsec (for higer resolution DEM)
   4. Change dropdown from "ArcGrid" to "GridFloat"
   5. Save Changes at the bottom of the page

Recomended Reading

Tarsier tutorial: Raster data

Tarsier tutorial: Raster resampler

Tarsier tutorial: Renderer

Tarsier tutorial: Simple fly-through

Introduction

In your ENVS 436remote sensing class you have developed and ground truthed a land cover map and an NDVI raster. You are now going to use that data in Tarsier. Export those two rasters from ERDAS in *.grd file format. Use your project folder to store all your Tarsier files.

Simplify the land cover map

Your land cover map has too many classes for our purposes. We will want to reclassify the map, distilling the classes down to just three: trees, shrubs, and other.

1. Open Tarsino
2. Open your Fort Ord land cover map:
   1. ->File ->Open
   2. Navigate to your *.grd format land cover map and double click the file (click yes when it asks if the file is from ERDAS)
   3. Flip your image so North is up Raster->Flip Vertically
   4. Save file as *.tra in you Tarsier folder inside your project folder (name appropriately)
   5. Click yes when asked to rename and save as Tarsier raster file
   6. Warning: Tarsier will now ask you to save multiple files
      1. Save as *.tra only once. Do not save the second *.tra!!!!!!!!!
      2. Save the *.trv with the same name, this saves the raster viewer (this will come in handy when saving a workspace later)
3. Open the Raster Lookup tool:
   1. ->File ->New ->Tools ->Raster Lookup
4. Load the land cover map into the Raster Lookup
   1. In the Raster Lookup view, use the drop down box next to Input Raster: to select your land cover map
5. Click the Find Values button
6. This will display a table with a column, Input, for all the values from the input raster (your land cover map) and another column, Output, that will dictate the new values for the reclassified map. If not to the right of Lookup Table Data:, click the View button.
7. Reclassify the map.
   1. Right now the "Output" column is filled with "-9999" which is the default null value. This will be the value of your "Other" class.
   2. For any input value that you think represent forest or trees, edit the corresponding output value by typing a "1" into the cell.
   3. For any input value that you think represent shrubs or chaparral, give the output value a "2".
8. After you have finished editing the table, click the Execute button on the Raster Lookup view.
9. View and save your reclassified raster
   1. To the right of Output Raster 0: click the View button
   2. Save the raster: With the Raster View window active, ->File ->Save As. . . Save your raster to an apropriate location. Tarsino will recognise file names up to 255 characters (no spaces), so name your file something informative like "'Original file name'_ReclassifiedTo.Trees.Shrubs.Other.'yymmdd'.tra".

Creating Raster Symbol Scheme

The reclassified map has three classes, one of which is null (Other). You now need to let Tarsier know how you want the non-null classes to be visually represented in a render. One way to do this is to create a symbol scheme.

1. Export your reclassified map to a Raster Symbol Scheme
   1. Make sure your the raster view window is active, if not click on it
   2. ->Raster ->Export to RasterSymbolScheme (This should open a new view window)
2. In the RasterSymbolScheme view you will see a list of all the non-null values from your reclassified raster. Click on unnamed 1 to edit its properties
   1. Recall that the value "1" is to represent trees, so in the box next to Tag type Trees
   2. Set the Max Height to something reasonable for a Fort Ord tree, maybe 7
   3. Click Load Texture and navigate to your Oak.bmp
   4. Set the Transparent Color bar to the background color of the *.bmp file to make it transparent
3. Similarly edit the properties for the shrub class (unnamed 2)
4. Save your raster symbol scheme

Visualizing Fort Ord with the Renderer

1. Open the Renderer
   1. ->File ->New ->Data Views ->Render view

  * At this point it might be a good idea to get your viewer windows the way you want them and save a workspace

1. Make and view the Fort Ord terrain
   1. On the Raster tab next to the Relief box, click Open
   2. Navigate to your Fort Ord DEM (UTM)
   3. Once it is loaded, click the Make next to Terrain
   4. Activate the Raster tab by clicking the check box at the upper left
   5. On the Cam 1 tab, click one of the camera icons on the left
2. Add the NAIP imagery
   1. On the Raster tab load the Fort Ord NAIP imagery into the Raster box (click Open and navigate)
   2. Click the C and check the RGB (true color)
3. Add in the land cover symbols
   1. On the Cvr tab, load the percent green cover raster into Cover (1k)
      1. Multiply this raster by 10000 raster->Algebra->multiply
   2. On the Sym1 tab, load the reclassified land cover raster into the Symbol raster box
   3. Load the RasterSymbolScheme into the Raster Symbol Scheme box
   4. Change the symbol scheme from "Sphere" to "User Defined"
   5. Check the box to the left of Symbol raster

Now fly around your virtual reality. This is done by going to the Cam 1 tab and clicking keys. You can then use the key controls to move your point of view.

Links

• Tarsier Tutorials