org.tinfour.gis.las

Class LasFileReader

java.lang.Object

org.tinfour.gis.las.LasFileReader

public class LasFileReader
extends Object

Reads the content of a LAS file. The file is divided into a header and a variable sized set of records each corresponding to a distinct lidar measurement. The header metadata is read by the constructor. The records must be read one-at-a-time through calls to the readRecord method.

This code is based on information that is given in LAS Specification Version 1.4-R13, 15 July 2013.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LasFileReader.CoordinateReferenceSystemOption Provides definitions for the alternate methods for specifying a coordinate reference system.

Constructor Summary

Constructors

Constructor and Description
LasFileReader(File path)

Method Summary

Modifier and Type	Method and Description
void	close() Closes all internal data files.
LasFileReader.CoordinateReferenceSystemOption	getCoordinateReferenceSystemOption() Gets the option that was used for storing the coordinate reference system in the LAS file.
File	getFile() Get the source file for the reader.
String	getFileSignature()
GeoTiffData	getGeoTiffData() Gets a copy of the GeoTiffData associated with the LAS file, if any.
LasGpsTimeType	getLasGpsTimeType() Gets the representation of time that is assigned to the sample point GPS time values.
LinearUnits	getLinearUnits() Get the linear units specified by the LAS file.
double	getMaxX() Gets the maximum value for the x coordinates of the points in the LAS file as specified in the LAS-standard file header.
double	getMaxY() Gets the maximum value for the y coordinates of the points in the LAS file as specified in the LAS-standard file header.
double	getMaxZ() Gets the maximum value for the z coordinates of the points in the LAS file as specified in the LAS-standard file header.
double	getMinX() Gets the minimum value for the x coordinates of the points in the LAS file as specified in the LAS-standard file header.
double	getMinY() Gets the minimum value for the y coordinates of the points in the LAS file as specified in the LAS-standard file header.
double	getMinZ() Gets the minimum value for the z coordinates of the points in the LAS file as specified in the LAS-standard file header.
long	getNumberOfPointRecords() Get the number of point records in file.
int	getPointDataRecordFormat() Get the record format specified in the LAS file.
LasScaleAndOffset	getScaleAndOffset() Gets the horizontal and vertical scale and offset factors that were read from the LAS file header.
LasVariableLengthRecord	getVariableLengthRecordByRecordId(int recordId) Gets the variable-length record with the specified recordId
List<LasVariableLengthRecord>	getVariableLengthRecordList() Gets a new instance of a list containing all variable length records.
void	readRecord(long recordIndex, LasPoint p) Read a record from the LAS file.
byte[]	readVariableLengthRecordBytes(LasVariableLengthRecord vlr) Read the content of a variable length record as a series of bytes.
double[]	readVariableLengthRecordDoubles(LasVariableLengthRecord vlr) Read the content of the Variable Length Record interpreting it as an array of double-precision floating-point values.
int[]	readVariableLengthRecordUnsignedShorts(LasVariableLengthRecord vlr) Read the content of the Variable Length Record interpreting it as an array of unsigned short integers.
String	toString()
boolean	usesGeographicCoordinates() Provides an incomplete and weak implementation of a method that determines if the LAS file contains a geographic coordinate system.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

LasFileReader

public LasFileReader(File path)
              throws IOException

Throws:

IOException

Method Detail

getFile

public File getFile()

Get the source file for the reader.

Returns:

a valid file instance.

readRecord

public void readRecord(long recordIndex,
                       LasPoint p)
                throws IOException

Read a record from the LAS file. The LasPoint object is used as a container to hold the results of the read. Since this method may be called literally millions of times, it is advantageous to reuse the point object rather than creating a large number of instances.

Note that depending on the record type used in the LAS file, not all elements may be populated.

Parameters:

recordIndex - the index of the record (0 to numberOfPointRecords-1)

p - a valid instance to receive data

Throws:

IOException - In the event of an unrecoverable IOException

getPointDataRecordFormat

public int getPointDataRecordFormat()

Get the record format specified in the LAS file. The meaning of this value is described in the LAS specification. Generally, the record format is more useful than the actual LAS format version of the file.

Returns:

a positive integer value.

toString

public String toString()

Overrides:

toString in class Object

getNumberOfPointRecords

public long getNumberOfPointRecords()

Get the number of point records in file.

Returns:

a positive long integer.

close

public void close()
           throws IOException

Closes all internal data files.

Throws:

IOException - in the event of an non-recoverable IO condition.

getFileSignature

public String getFileSignature()

Returns:

the fileSignature

getMinX

public double getMinX()

Gets the minimum value for the x coordinates of the points in the LAS file as specified in the LAS-standard file header.

Returns:

the minimum value for the x coordinates in the file

getMaxX

public double getMaxX()

Gets the maximum value for the x coordinates of the points in the LAS file as specified in the LAS-standard file header.

Returns:

the maximum value for the x coordinates in the file

getMinY

public double getMinY()

Gets the minimum value for the y coordinates of the points in the LAS file as specified in the LAS-standard file header.

Returns:

the minimum value for the y coordinates in the file

getMaxY

public double getMaxY()

Gets the maximum value for the y coordinates of the points in the LAS file as specified in the LAS-standard file header.

Returns:

the maximum value for the y coordinates in the file.

getMinZ

public double getMinZ()

Gets the minimum value for the z coordinates of the points in the LAS file as specified in the LAS-standard file header.

Returns:

the minimum value for the z coordinates in the file.

getMaxZ

public double getMaxZ()

Gets the maximum value for the z coordinates of the points in the LAS file as specified in the LAS-standard file header.

Returns:

the maximum value for the z coordinates in the file.

getCoordinateReferenceSystemOption

public LasFileReader.CoordinateReferenceSystemOption getCoordinateReferenceSystemOption()

Gets the option that was used for storing the coordinate reference system in the LAS file. This information will indicate the appropriate interpretation of the associated variable-length record instance.

Returns:

a valid enumeration instance.

getVariableLengthRecordList

public List<LasVariableLengthRecord> getVariableLengthRecordList()

Gets a new instance of a list containing all variable length records.

Returns:

a valid list.

getVariableLengthRecordByRecordId

public LasVariableLengthRecord getVariableLengthRecordByRecordId(int recordId)

Gets the variable-length record with the specified recordId

Parameters:

recordId - a valid record ID in agreement with the LAS specification

Returns:

if found, a valid instance; otherwise, a null

readVariableLengthRecordBytes

public byte[] readVariableLengthRecordBytes(LasVariableLengthRecord vlr)
                                     throws IOException

Read the content of a variable length record as a series of bytes.

Parameters:

vlr - a valid variable length record from the current file

Returns:

an array of bytes dimensions to the size of the record content (excluding record header)

Throws:

IOException - in the event of an unsuccessful read operation

readVariableLengthRecordUnsignedShorts

public int[] readVariableLengthRecordUnsignedShorts(LasVariableLengthRecord vlr)
                                             throws IOException

Read the content of the Variable Length Record interpreting it as an array of unsigned short integers. The LAS Specification calls for all data to be stored in little-endian byte order.

Parameters:

vlr - a valid instance

Returns:

an array of zero or more integers.

Throws:

IOException - in the event of an unrecoverable I/O error.

readVariableLengthRecordDoubles

public double[] readVariableLengthRecordDoubles(LasVariableLengthRecord vlr)
                                         throws IOException

Read the content of the Variable Length Record interpreting it as an array of double-precision floating-point values. The LAS Specification calls for all floating-point data to be stored as IEEE-754 floats in little-endian byte order.

Parameters:

vlr - a valid instance

Returns:

an array of zero or more double-precision floating point values.

Throws:

IOException - in the event of an unrecoverable I/O error.

usesGeographicCoordinates

public boolean usesGeographicCoordinates()

Provides an incomplete and weak implementation of a method that determines if the LAS file contains a geographic coordinate system. At present, this result is obtained by inspecting the range of the x and y coordinates. However, a valid implementation would involve looking at the projection-related information in the Variable Length Records as defined by the LAS specification.

Returns:

true if the LAS file uses geographic coordinates, otherwise false.

getLasGpsTimeType

public LasGpsTimeType getLasGpsTimeType()

Gets the representation of time that is assigned to the sample point GPS time values. This option is arbitrarily assigned by the agency that collected and distributed the LAS file. It is necessary to use this value in order to interpret the GPS time of the samples.

Returns:

an enumeration giving the time recording format used for the LAS file

getGeoTiffData

public GeoTiffData getGeoTiffData()

Gets a copy of the GeoTiffData associated with the LAS file, if any. For those LAS files which use Well-Known Text (WKT) specifications, the return value from this method will be null.

Returns:

if available, a valid instance; otherwise a null.

getLinearUnits

public LinearUnits getLinearUnits()

Get the linear units specified by the LAS file. This method assumes that the vertical and horizontal data are in the same system (unless Geographic coordinates are used). In the future this assumption may be revised, requiring a change to the API.

Returns:

a valid instance of the enumeration.

getScaleAndOffset

public LasScaleAndOffset getScaleAndOffset()

Gets the horizontal and vertical scale and offset factors that were read from the LAS file header. Normally, these factors are applied to coordinates when they are read using the readRecord() method and are not needed by applications. But for those applications that have other requirements, this API exposes the header data elements.

Returns:

a valid instance.