StreamBuilder

Frequently Asked Questions

If you are experiencing problems using StreamBuilder, please refer to the topics below.  These may assist in getting the required data into or results out of StreamBuilder.

1.  How much memory do I need or How big a DEM can I process ?

The amount of memory that StreamBuilder requires depends on the size of the DEM that you are processing.  StreamBuilder will use as much of your computer's RAM as it needs to, and will then use virtual memory if there is insufficient RAM.

The amount of virtual memory available to applications such as StreamBuilder is controlled using Control Panel > System  and choosing the  Advanced or Performance tab.  The maximum amount of virtual memory you can allocate depends on the free space on your computer's disk.

As an approximate guide, StreamBuilder's maximum memory usage (in bytes) can be estimated as number of rows in DEM x number of columns in DEM x 15.  So for a 1000 x 1000 DEM, StreamBuilder may need as much as 15MB RAM.  This is in addition to the memory used by Windows, MapInfo Professional and any other applications that are running.

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2. Can I use my Vertical Mapper grid in StreamBuilder ?

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3. Why can't my ER Mapper dataset be read by StreamBuilder ?

Check the following:

1. Open the <dataset>.ers file in ER Viewer (free and downloadable from www.ermapper.com)
2. If the .ers file views OK in ER Viewer, but StreamBuilder, reports that it "cannot read virtual dataset", then you will need to convert the virtual dataset into a real disk file using ER Mapper.

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4. How can I speed up the catchment processing using StreamBuilder ?

A number of parameters can affect the speed with which StreamBuilder processes drainage data.  Some or all of the points listed below may help optimize your use of StreamBuilder.

1. Read only the relevant portion of the DEM by choosing the Use all DEM data in front window option.
2. If you don't need sub-basins and streams, then choose the One Basin option and turn off Construct Stream Network. Building the stream network involves a considerable extra amount of processing.
3. If you don't need to store flow direction and upslope area grids, then turn off the Store processed grids option.
4. If generating sub-basins, ensure that the Minimum Basin Area is not too small.

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5. Why does my DEM grid not align correctly with drainage created by StreamBuilder ?

This can occur if the DEM grid is not registered correctly.  MapInfo will always display a grid as a rectangular bitmap (irrespective of any registration errors), but will always project polylines and regions to their correct location.

Examine the registration points in Table > Raster > Modify Image Registration.  There should be 4 control points, one in each corner of the grid, and MapInfo should show a registration error of 0 pixels.  If the grid is registered with 3 control points, located close together (for example at cells 0,0 1,0 and 0,1) then you may need to modify these control points to grid corners.

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6. How do I process a grid format not supported by MapInfo or StreamBuilder ?

You will need to convert your grid format to one of the formats supported by MapInfo or StreamBuilder.  Software that reads and writes your grid format will usually have an option to export or save as ASCII xyz.  Use this option and then import the xyz grid into StreamBuilder.

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7. How do I use my table of Contour Lines with StreamBuilder ?

Contour lines cannot be used directly with software such as StreamBuilder which require a regular grid of elevation values stored in a recognized grid format.  In order to convert your contour lines into a grid, you will need to extract the easting, northing and elevation values for each node in each contour polyline using one of a number of commercially or freely available tools.

You will then need to grid the table of elevation points using MapInfo or other software with grid interpolation capabilities.

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8. How do I know how much flow there is in my stream network ?

StreamBuilder generates a stream network which corresponds to the natural flow lines that free surface water would follow.  Whether or not these lines correspond to actual surface streams depends upon climate (precipitation levels and temperature) as well as surface characteristics (such as soil permeability and vegetation) and cultural influences (such as upstream diversion).

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9. Will my StreamBuilder licence be valid if I upgrade or re-install MapInfo Professional ?

The licence for StreamBuilder is stored in the MapInfo Professional program directory.  If you wish to move your installation of MapInfo Professional to a different directory then you must transfer your StreamBuilder licence to diskette before the move and then import afterwards.  If you are upgrading MapInfo Professional, then the StreamBuilder licence will remain valid if the upgrade is installed into the same directory.  Otherwise transfer to diskette and then import when you have installed the upgrade.

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10. Why is my drainage network not continuous ?

If the drainage network that StreamBuilder creates is discontinuous, then this is probably because it is finding breaks in the flow directions.  The flow discontinuities may arise from the interpolation method used to create the DEM.  If you pre-process the DEM to fill depressions then StreamBuilder modifies the DEM to ensure there is continuous flow from high points (sources) to low points (sinks).

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