Page History

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The BIL, BIP and BSQ raster data formats were originally developed by USGS for CCT tape formats for to store Landsat satellite data from 1972 on. These are simple uncompressed binary files representing a raster of one or more image bands, accompanied by an ASCII header file (*.hdr) with image information. The main file extension depends on the format, or storage sequence:

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The PI implementation of BIL files however includes several adaptations to specific FEWS purposes (i.e. using floating point data, extension for time series using blocks) which causes this FEWS implementation to not fully comply with the official specifications of the BIL format and changing this structure and lack support for BIP and BSQ format files. Changing this implementation would break backward compatibility so it was decided to create a new parser, which als also properly supports the BIL, BIP and BSQ format.

This new implementation is fully compliant with the ESRI technical specifications , but does NOT offer specific FEWS extensions to the format for dealing with time series or floating point pixel values, this new importer and can be configured with the new "BILBIPBSQ" identifier, whereas the existing PI implementation of FEWS BIL files uses the identifier "BIL".

Using NBLOCKS for time series

For many applications multiple BIL, BIP or BSQ files could be available, representing a time series of observations (daily, monthly, weekly, etc.)

In order to be able to import such a time series of Images, the binary image files can be appended into a single file in chronological order where the original files become so-called "blocks" in the combined image file. In this case an extra field NBLOCKS is added to the header file to indicate the number of time steps in the combined image and an extra (*.tim) file is added to provide a date/time stamp for each block.

Appending the binary image files to create a time series can be done using (for example) a DOS copy command in binary append mode, as follows:

	copy /b step1.bil+step2.bil+step2.bil+step4.bil 4steps.bil

Configuration

	<location id="SATH_AFRICA" name="SATH_AFRICA">
		<shortName>SATH_AFRICA</shortName>
		<x>0</x>
		<y>0</y>
	</location>

	<regular locationId="SATH_AFRICA">
		<description>SATH Rainfall files</description>
		<rows>702</rows>
		<columns>1002</columns>
		<geoDatum>WGS 1984</geoDatum>
		<firstCellCenter>
			<x>-13</x>
			<y>25</y>
			<z>0</z>
		</firstCellCenter>
		<xCellSize>.03</xCellSize>
		<yCellSize>.03</yCellSize>
	</regular>

<idMap >
   <parameter internal="P.obs" external = "0"/>
   <parameter internal="T.obs" external = "1"/>
</idMap>

<timeSeriesImportRun>
   <import>
      <general>
         <importType>BILBIPBSQ</importType>
         <folder>$IMPORT_FOLDER$\BSQ</folder>
         <fileNameObservationDateTimePattern>'NI_'yyyyMMdd'.BSQ'</fileNameObservationDateTimePattern>         
         <idMapId>IdImportBSQ</idMapId>
         <unitConversionsId>ImportUnitConversions</unitConversionsId>
         <importTimeZone>
            <timeZoneOffset>+00:00</timeZoneOffset>
         </importTimeZone>
         <geoDatum>WGS 1984</geoDatum>
         <dataFeedId>SATH_AFRICA</dataFeedId>
      </general>
      <timeSeriesSet>
         <moduleInstanceId>ImportBSQ</moduleInstanceId>
         <valueType>grid</valueType>
         <parameterId>P.obs</parameterId>
         <locationId>SATH_AFRICA</locationId>
         <timeSeriesType>external historical</timeSeriesType>
         <timeStep unit="day"/>
         <readWriteMode>add originals</readWriteMode>
         <expiryTime unit="day" multiplier="30"/>
      </timeSeriesSet>
         <timeSeriesSet>
         <moduleInstanceId>ImportBSQ</moduleInstanceId>
         <valueType>grid</valueType>
         <parameterId>T.obs</parameterId>
         <locationId>SATH_AFRICA</locationId>
         <timeSeriesType>external historical</timeSeriesType>
         <timeStep unit="day"/>
         <readWriteMode>add originals</readWriteMode>
         <expiryTime unit="day" multiplier="30"/>
      </timeSeriesSet>
   </import>
</timeSeriesImportRun>