GPS Data Sources and File Types

A list of supported file types and how to import them into ReefMaster.

Transferring Data From a GPS Device

Before data can be imported into ReefMaster it must first be transferred from the source device.

The most common method of transferring data from a physical GPS/Sounder device is via a Memory Card.

·Consult the documentation that came with your GPS device for information on how to transfer data onto a memory card. For later model Humminbird units, for example, there is an option Export All Nav Data which transfers all saved tracks and waypoints.

·Once data is has been transferred onto a memory card, the card should be connected to the PC that is running ReefMaster. Although the data can be imported directly into ReefMaster from a connected memory card, it is recommended that data is first transferred to the hard-disk on the PC, where it can be stored, and is available for re-import to ReefMaster if required.

·If the file type of the data from the GPS unit is not directly supported by ReefMaster, it must be converted into a format that is. For example, native Garmin data must be converted to the GPX format using the Garmin HomePort software package.

Supported File Types

ReefMaster is able to read a range of file types containing track and waypoint data.

Sonar Log Files

·Sonar log files contain latitude, longitude, depth and time information for each track point, as well as the raw sonar data from each sonar ping and, often, further information such as water temperature, boat speed and course. As sonar log files contain so much more information than GPS track files, they are the preferred source of data when creating maps.

·As track points imported from sonar log files contain explicit time information, the Equipment Profile option Regular Trackpoint Interval is ignored during the import process for these file types.

·Consult your GPS/sounder unit documentation for information on how to record sonar log files.

Humminbird™ Sonar Logs

Humminbird units log sonar to data files within a directory named RECORD. Within this directory there is a .DAT file for each sonar recording that has been made, along with a sub-directory of the same name, which contains the actual sonar recording files.

For example, a recording named R00160 will have a file named R00160.DAT and a sub-directory named R00160. The sub-directory contains a series of .SON sonar log files, one for each recorded sonar channel. On a side imaging unit, for example, you might find four .SON files named B0000.SON through B003.SON. Typically, the zero numbered file contains 83khz data, number one contains 200khz data and two and three hold the left and right channels of the side imaging data. ReefMaster only imports data from the 200khz channel.

·To import a Humminbird sonar log, select the .DAT file in the RECORD directory. ReefMaster will locate and load the appropriate .SON file.

Note that older (pre v4.x) versions of the Humminbird sonar log file format do not contain depth information and are not supported by ReefMaster.

Lowrance™ Sonar Logs (.SLG and .SL2) Files

Lowrance™ units do not save depth information with track logs, so sonar logs must be used to provide the depth information required for mapping.

Lowrance units log sonar in one of two file formats; SLG and SL2. The SL2 file format is the preferred option for use with ReefMaster.

SLG Files

SLG files contain sonar pings for a single channel of sonar. When logging sonar on the Lowrance device, you must specify which channel to record. The preference for ReefMaster import is the highest frequency channel. For example, if using a dual frequency sonar with 83khz and 200hkz channels, choose 200khz.

SL2 Files

SL2 files can contain sonar pings for more than one channel, and may also include side-scan data. SL2 files are the preferred choice when logging data for use in ReefMaster.

ReefMaster can import both SLG and SL2 files directly, and is also able to import files generated with the Lowrance™ utility slg2txt.exe. If Lowrance sonar logs are not imported correctly by ReefMaster, try installing slg2txt and checking the option Use slg2txt in the current Equipment Profile. This will force ReefMaster to use the Lowrance utility when importing Lowrance sonar log files.

NMEA Log Files

Text files containing logs of NMEA 1083 messages, with the extensions .txt or .log, can be imported as tracks.

Position and depth messages must be contained within the same file, as NMEA depth messages do not contain time information and it is therefore not possible to interleave log files from separate NMEA devices after they have been recorded.

ReefMaster can obtain information from position messages RMC, GGA and GLL, heading messages HDG, HDM, HDT and VTG and depth messages DPT and DBT.

A new track-point is created for each change of position, which is assigned the last processed depth value. If no depth messages have been processed, the track-point is created with zero depth. A transducer position offset is applied if it has been set in the current Equipment Profile; the heading used for this calculation is derived from RMC or heading messages if available, otherwise the heading is calculated by using the last two known positions.

GPS Track and Waypoint Files

GPS track and waypoint files can be exported from some GPS units; e.g. Humminbird units can export saved tracks and waypoints in HT and HWR format files, whilst Lowrance units produce USR files than contain both waypoints and tracks.

GPX (GPs eXhange)

The GPX file format is a common file format for the exchange of GPS data between different device manufacturers.

The standard GPX format supports waypoints and track logs, but does not contain depth information for individual track points.

Humminbird™ and Garmin™ provide their own extensions to the GPX track format which do include the depth of each track point. Tracks contained in GPX files generated by Humminbird™ or Garmin™ devices can be used to generate maps, so long as the depth information is present. Tracks contained in GPX files from Lowrance™ units cannot be used to create maps, although they can be imported as zero-depth tracks.

GPX track files do not contain time information for individual track points. If time information is required - for example, to apply an accurate tide offset - then the option Regular Trackpoint Interval must be set in the Equipment Profile used during import. The time interval should correspond to the device setting used whilst the track was created.

CSV (Comma Separated Values)

CSV files are text files that hold a set of within each row. Individual values are commonly separated by commas, but can also be separated by other characters such as TAB, or SPACE.

See Importing Data from Text Files for more.

Humminbird™ Track (.HT) and Humminbird™ Waypoints and Routes (.HWR) files

Humminbird GPS/Sounder units export tracks and waypoints to two separate file types, Humminbird Track (.HT) and Humminbird Waypoints and Routes (.HWR) files. A separate .HT file is produced for each track that has been saved in the unit (typically up to a maximum of 50). These files have the name 00.HT through [XX].HT, where [XX] is the number of saved tracks on the unit. A single .HWR file is produced containing all of the waypoints and routes in the system. These files are stored in a folder called MATRIX which is positioned at the root of the memory card.

HT track files do not contain time information for individual track points. If time information is required - for example, to apply an accurate tide offset - then the option Regular Trackpoint Interval must be set in the Equipment Profile used during import. The time interval should correspond to the device setting used whilst the track was created.

Note that there is a bug present on many older Humminbird™ units that resets track-point depths to zero once the current track has filled (about 21000 track-points) and started overwriting from the beginning. Once this has happened, all depths associated with the existing current track are lost and cannot be retrieved. This problem can be mitigated by saving areas of interest into one of the available saved track positions as they are recorded, or in any case before the maximum number of track-points has been exceeded. At a one second track-point interval, a single Humminbird™ track provides approximately six hours of recording time.

Humminbird™ .DAT Screen Snapshot Files

Some Humminbird™ devices can be configured to save a snapshot image of the unit's screen to file every time a new waypoint is created. This option can be very useful for recording extra information with a waypoint, such as the view of the 2D or side imaging sonar at the time. Humminbird™ saves a data file with waypoint location information, with the extension .DAT, alongside the image file in a folder named SNAPSHOTS, stored at the root of the memory card.

ReefMaster imports .DAT files as individual waypoints, along with the associated image file, which is stored as a waypoint image.

Lowrance™ .USR Files

Lowrance™ units can export waypoints and tracks in a Lowrance™ proprietary file format with the extension .USR. USR files come in several versions; ReefMaster is only able to read versions 2 and 3. Units that write version 4 USR files are usually able to also export data in GPX file format, which should be used in preference.

Tracks within USR files do not contain depth information and so cannot be used for creating maps.

ESRI Shapefiles

Polygons and lines held within ESRI Shapefiles can be imported as tracks or map boundaries. Attributes belonging to shapefiles are not imported. Track point depths can be obtained from 3D shapes that contain Z values for each coordinate. In this case, depths are assumed to be in metres. Two dimensional shapefiles are imported as tracks with a uniform depth of zero.

If the shapefile to be imported has an associated projection, then ReefMaster will re-project non-WGS84 projections to WGS84.

If the shapefile does not have an associated projection, then the shapefile is assumed to be WGS84. Importing a non-WGS84 shapefile without an associated projection file will give unpredictable results.