You will need:
- The SD Card from the TAR-3 Resistance Meter
- Your results! The results are copied to the TAR3DATA.TXT file at the end of the grid and saved onto the SD Card.
- A PC with the 'Snuffler' software
- You can download a copy of 'Snuffler' software from here.
- Your notes!
- When using the TAR-3 Resistance Meter you should make a note of the order you survey the grids and the direction(s) you traverse the grids.
You should also record the survey's position/location so that you can identify the position of any anomalies on the ground.
The TAR3DATA.TXT File
- Download the Snuffler software from here.
- Unzip/Extract the compressed file into a folder. (The default is 'Snuffler').
- Run (install) the program
- You may be asked to confirm that you want to install/run the software. If you have downloaded the software from here, install the software. Do not download Snuffler from unofficial websites! Follow the instructions/prompts and install the software.
- Run Snuffler
- Open the Snuffler program.
- Create a new project
- You create a new project using the
File::New Projectcommand on the menu bar – name the project eg. Test_Date
- Copy your data file into the project folder, Test_Date
- Insert the micro SD Card into the 'micro SD Card to standard SD Card adaptor' or into the 'micro SD Card to USB reader' and plug it into your PC. Navigate to the 'Removable Disk' and copy the TAR3DATA.TXT file into the projects folder (eg. Test_Date).
- Import your Grid Data
- Use the
File::Import From File::Import Frobisher Data Filecommand to import your data. (Read the section below regarding importing grids and grid numbering).
survey team has planned to survey a field. In the office they positioned their grids as shown above. To 'Geo Reference' their grids (and to find them again) they need to know the position of the grids. They can do this if they know the position of two points. (X1,Y1 and X2,Y2, see above). The two positions may be 'surveyed in' or be fixed points (such as a wall, Trig point, or other feature that can be identified in the future) and are used to locate one of the axis, see below.
The grids can be aligned in any direction and the user can survey them in any order. The surveyor can start in any corner and walk in any direction. It is important to record:
- The grid (A, B, C etc)
- The start corner (NW, SW, NE, or SE)
- The direction of each traverse (N, S, E, or W)
- The Grid Number of the TAR-3 Meter
The selection of reference/fixed points is outside the scope of this application note.
Grid Numbering and Identification
A geophysical survey team complete six grids in the following order N, O, P, L, J, and K. If the SD Card was formated in a PC before starting the grids would be numbered 1, 2, 3, 4, 5, and 6 and N=1, O=2, P=3, L=4, J=5, and K=6. When importing grids into Snuffler the software numbers the grids in a file sequentially, beginning at 1.
To prevent users deleting data, the TAR-3 Resistance Meter automatically increments the GRID No – users cannot delete grids using the TAR-3 Meter. Grids can only be deleted using a PC!
If the TAR-3 Resistance Meter had been used before, and the SD Card contained results from a previous survey, then the grids would be numbered sequentially, continuing from the previous grid number. Users cannot set or change the grid number. It is automatically set and updated by the TAR-3 unit. If the TAR3DATA.TXT file is deleted (using a PC) before starting a new grid the file is created and the results from the new grid(s) appended to it.
- The TAR-3 meter and SD Card were used the day before.
- Four grids were completed and saved to the card.
- The TAR3DATA.TXT file was copied to a PC
- No files were deleted from the SD Card
The following day the same SD Card is used and:
- The geophysical survey team complete six more grids.
- The grids are in the following order N, O, P, L, J, and K.
- These grids are numbered 5, 6, 7, 8, 9, and 10 (N=5, O=6, etc.).
- The TAR3DATA.TXT file will contain the results from 10 grids.
- The last six grids are today’s grids and grid K is the last one.
Before importing the grids users may delete unwanted grids from a copy of the TAR3DATA.TXT file.
If the first four grids are deleted from a copy of the TAR3DATA.TXT data file and the file imported it to the project the software will renumber them 1 to 6!
During the import process users enter the start position and direction of travel once – this setting is used for all grids in the file. If different start points have been used (or different traverse directions), the grids must be imported separately. Cut and paste each grid into a new file – remember that each file must begin and end with a blank line
In a Snuffler project, each grid must be the same size if they are to be 'mapped' to the same 'view'
Analysing the Data
When the data is imported, a new Map File must be created
File::New::Map File In the example above it could be 4 by 4 (ready for extra grids) or 3 by 2 for the six grids surveyed.
Right clicking the Map File allows the user to
Spawn Main View and see their results (in black and white or multi colour.)
Display::Display Settings (alt-d) shows the distribution of readings. There may by a few outliers (sometimes hundreds or thousands of Ohms different from the average) They may be the result of a wall above the ground surface or the result of 'poor' technique. Users should refer to their notes to decide if the readings should be deleted, marked as a 'Dummy' or edited.
© RM Frobisher (1986) Ltd. 2015 - . All rights reserved