Common errors, exceptions and warnings
Contents
Common errors, exceptions and warnings#
A description of some of the more common errors and exceptions follows, with some help to resolve the specific issues.
Errors and Exceptions#
Commandline Exception#
These occur when there are problems with parsing options and arguments from the command line of a Geona Hyperspectral utility. A simple description of the problem will follow the exception and this is usually enough to help resolve the issue.
BinaryReader Exception#
These occur when reading from BIL or BSQ files. A description of the problem will follow the exception.
FileWriter Exception#
These are thrown when there is a problem writing to files. A description of the problem will follow the exception.
Unrecognised options on command line#
This message occurs when an option has been specified to Geona Hyperspectral which does not exist.
File does not exist#
This error happens when a file has been requested to be used but the file does not exist (or it is not at the path Geona Hyperspectral is expecting).
Filesize from header: <number> does not agree with filesize from disk#
This occurs when the BIL or BSQ file is not the size that the accompanying hdr file expects. The size is calculated from the header file as lines * samples * bands * size of data type. If this error is thrown then check that the correct files are being used. It could also be a sign that some part of the processing has failed or stopped leaving a corrupt half-written file.
DEM Unsupported#
Error messages that begin with this imply that the digital elevation model (DEM) being used is not in a format that is currently supported. The DEM should be a single band BIL or BSQ file, contain a “map info” string in the hdr file that defines a Geographic Latitude/Longitude projection in the WGS84 datum. Geona includes methods for converting existing DEMs into a suitable format and for creating new DEMs from different data sources. See the pages on digital elevation models. The elevation should be height above the WGS84 ellipsoid.
There is not enough available disk space for this data file#
This message is thrown when created a georectified map if it is calculated that the file to be written is larger than the amount
of disk space available. If you disagree then you can ignore the message by selecting -ignorediskspace in command line usage
or the option to ignore the exception from the Geona dashboard. Note however that if there is not enough disk space then it will fill
up the disk before completing writing the file.
Warnings#
Warnings are messages that do not break or stop the processing but may result in an erroneous output and are thrown if it looks like there may be a mistake with the data or commands being used. Often these can be safely ignored, and are just for information, but some will warrant further investigation. Some of the more common ones are given below.
Maximum interpolation distance is large compared to pixel spacing [approx nadir pixel spacing:#
This message is thown in the map generation stage of the processing. It means that the distance used in the interpolation algorithms for the resampling is large compared to the ground distance between neighbouring pixels. This will affect the speed of the processing. For example, if the resampling algorithm is nearest neighbour and pixels are spaced approximately 2 metres apart but the algorithm is searching for pixels within a 500 metre radius, then many more pixels need to be searched than are required. However, the search distance has to be large enough that it does not leave empty holes where there are no points found within the radius.
Given pixel size appears very large compared to data resolution of IGM file. Are you sure the pixel size is in the correct units for the IGM file?#
This warning message is thrown in the map generation stage when the pixel size to create a map for is very large compared to the data in the IGM. One reason this message can be thrown is if the IGM file is in geographic coordinates (degrees) but the map pixel size has been given in metres. It is important to always define the map pixel size in the same coordinate system as the IGM file. E.g. if the IGM is in metres then define the pixel size in metres.
Warning - no Digital Elevation Model was given on command line. Will map to ellipsoid surface.#
This message is thrown in the geocorrection stage when no digital elevation model is being used. It is a warning as with no DEM the accuracy of the geolocation is much reduced. If you wish to map to the ellipsoid surface then this is fine and nothing needs to be done.