The LEA Map Object and Location Record Objects

Version: 3.4

• Introduction
• Recognised Formats
• Map Attributes
• Location Record Attributes
• Map Object Viewer

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Introduction

The LEA Map Object encompasses data displayed as a map, and is implemented in the DLL MAPCOM.DLL. See The LEA Object for information about how to add to the formats recognised and attributes read. The Location Record Object is used in conjunction with other LEA Objects to provide location reconciliation.

Map Formats

The LEA Map Object can recognise and read the following formats:

• ESRI Shape files
• UKOOA ASCII files (Lynx LOC)
• UKOOA EBCDIC files
• UKOOA files (DOS-delimited)
• UKOOA files (UNIX-delimited)

ESRI Shape files

ESRI shape files are used by ESRI Arcview to display map data. Shape files must have three component files with extensions shp shx and dbf present in the same directory. If any of the file components are not present, then the shape file is invalid. Shape files store one 'layer' of data, which can be made up of point, line or polygon vectors. Data is stored in one coordinate system, so if the shape file contains X-Y (or UTM) coordinates instead of latitude/longitude values, then the projection system cannot be determined, and is set to UNKNOWN.

UKOOA ASCII files (Lynx LOC)

Lynx-variant UKOOA files (LOC files) are an extension of the UKOOA P1/84 standard, stored as non-delimited ASCII.
Lynx LOC files are used by LEA applications, mainly to store seismic survey location information, but also for other related cultural information. Location data is can be stored both as latitude/longitude and as projected X-Y (UTM) coordinates, and information on the current projection system is stored in the file header, so if present, this information is read from the file.

UKOOA EBCDIC files

The standard UKOOA P1/84 standard for storing seismic location data. Each record is 80-bytes, blocked into 10-record groups of 800 bytes. When transcribed onto disk, all blocks are concatenated together into one file.

UKOOA files (DOS-delimited)

This is a variant of UKOOA that is stored as ASCII delimited by CR-LF pairs at the end of each record, making it suitable for display using standard DOS text-editing utilities.

UKOOA files (UNIX-delimited)

This is a variant of UKOOA that is stored as ASCII delimited by a LF character at the end of each record, making it suitable for display using standard UNIX text-editing utilities.

Map File Attributes

The LEA Map Object will attempt to read the following attributes:

• Title
• Region
• Minimum latitude (decimal degrees)
• Minimum longitude
• Maximum latitude
• Maximum longitude
• Minimum Easting (UTM X coordinate)
• Minimum Northing (Y)
• Maximum Easting (X)
• Maximum Northing (Y)
• Projection Information
• Number of layers
• Number of objects
• Base Map - true if the map stores seismic locations
• Object Name Field - for tabular formats, this is the number of the field used to store the Object Name.
• LatLon Coordinates - true if the map contains geographical (latitude/longitude) coordiantes.
• XY Coordinates - true if the map contains projected (X/Y) coordinates

Attributes are defined in the INI file MAPOBJ.INI.

Location Record Attributes

The LEA Location Record Object will attempt to read the following attributes for each object in a map file

• Record Name
• First Measure
• Last Measure
• Min Latitude
• Min Longitude
• Max Latitude
• Max Longitude
• Min X
• Min Y
• Max X
• Max Y
• Line Length (km)
• Polygon Area (sq km)
• First X
• First Y
• First Latitude
• First Longitude
• Last X
• LastY
• Last Latitude
• Last Longitude

Attributes are defined in the INI file LOCOBJ.INI. The Location Record Object is used by Florence and Zebedee to provide location reconciliation of other objects.

Map Object Viewer

The default viewer for map objects is BASEVIEW.

See also
[ The Lynx Exploration Archive Object ]
[The LEA Reconciliation Object]
[Florence - Catalogue Builder]
[Zebedee - Reconciler and GIS Loader]