|
A link with the collar was
established and the position and almanac information, as well as the schedule
for position fixes, was sent to the collar. The first fix must be obtained
within 10 minutes or the VHF beacon will switch into “Recovery” mode.
Deployment
 |
The Lotek GPS_2200L(R) collars
were fitted on two randomly selected sheep as they were off-loaded from
the livestock shipping trucks. The permittee used a shepherd’s crook to
select and control the sheep. The collar strap was quickly looped around
the animals’ necks and secured with holding plates and lock nuts tightened
to the specified 1.7 N×m torque. The collars were adjusted on both
sides to center the antenna on top. The sheep were marked with colored
chalk to distinguish them within the band, and then were released. |
Active Use
The Sawtooth NRA did
not possess a VHF receiving antenna and assumed it could monitor the sheep
by visual observation during allotment administration. The agency arranged
to borrow an antenna from a sister agency if needed. Within a week, one
of the collared sheep was missing. An antenna was obtained and the ewe
was shortly found with a broken leg. The “recovery” beacon pulse was never
heard, suggesting she continued sufficient movement to maintain the “normal”
beacon.
| No other problem was encountered.
The chalk quickly wore off, and the VHF antenna was the only means to monitor
the status of the sheep and their collars. The VHF antenna also proved
to be a very effective tool in monitoring the band location, whether nearby
and visible, or more distant. If visual identification is important, a
more durable product, such as marking paint, may be required. |
 |
The effect of fleece growth
through the season on the fit of the collar was a speculated concern initially,
but proved to be of no consequence. The collar remained snug on the neck,
and the fleece accumulated around it. No interference with the satellite
signal was apparent.
Incidentally, the sheep’s
leg was likely broken during the permittee’s scuffle to capture and constrain
the sheep initially to attach the collar. The herder had noted the sheep
limping as she walked away after the collar was attached. Care in such
occasions is obviously important to avoid injury to the animal as well
as to the handlers.
 |
Retrieval
The collars were collected
without difficulty on October 12 by the permittee. Close inspection of
the collar straps and unit housings found no compromised conditions beyond
normal wear. In contrast to some pretest concerns, the collars appeared
to be very durable.
The process to retrieve
the data from the collars was a reverse of the initial launching. Once
connected to the PC through the download link unit, the data was collected
from both collars without incident.
Post Processing
The data was exported from
the Lotek GPS_2000 Host software to a Microsoft Excel® spreadsheet.
Once in Excel, the data was corrected, analyzed, and prepared for further
analysis in the Geographic Information System (GIS).
|
The Lotek collar stores latitude
and longitude positions in degrees, minutes, and decimal seconds (to thousandths).
When exported from the host software via the spreadsheet option, the values
are converted to integer milliseconds. (See table 3.)
Table 3-Sample of the core data
as exported from the GPS_2000 Host software.
|
Latitude
|
Longitude
|
Height
|
Date
|
Time
|
DOP
|
Fix Status
|
SAT
ID |
|
158111287
|
-413337179
|
2167
|
6/7/2001
|
8:00:35
|
2.4
|
3D Fix
|
02
04 05 07 09 24 |
|
158082353
|
-413349224
|
2187
|
6/7/2001
|
10:00:39
|
2.7
|
3D Fix
|
04
05 06 10 24 30 |
|
158083601
|
-413356270
|
2184
|
6/7/2001
|
12:00:49
|
2.3
|
3D Fix
|
06
10 15 17 24 30 |
|
158086535
|
-413361563
|
2184
|
6/7/2001
|
14:00:36
|
4.3
|
2D Fix
|
06
15 17 |
|
158076787
|
-413350297
|
2184
|
6/7/2001
|
16:00:41
|
1.4
|
2D Fix
|
03
14 15 18 21 23 |
To prepare the data for analysis
within the GIS the millisecond latitude and longitude values were converted
to decimal degrees by dividing the milliseconds values by 3,600,000 (60
minutes x 60 seconds x 1000). (See table 4.)
Table 4-Sample of the
Latitude and Longitude conversions performed in the spreadsheet.
|
Latitude millisecond
|
Latitude
decimal degrees
|
Longitude millisecond
|
Longitude
decimal degrees
|
|
158111287
|
43.91980194
|
-413337179
|
-114.81588306
|
|
158082353
|
43.91176472
|
-413349224
|
-114.81922889
|
|
158083601
|
43.91211139
|
-413356270
|
-114.82118611
|
|
158086535
|
43.91292639
|
-413361563
|
-114.82265639
|
|
158076787
|
43.91021861
|
-413350297
|
-114.81952694
|
Simple formatting and heading
changes were then also applied to a few of the remaining fields for compatibility
with the GIS. The result was saved in dBase IV® format.
ArcView GIS® version
3.1 was used to create a geographic theme for analysis from the table of
position values (i.e., an “Event Theme”). For compatibility with the Sawtooth
National Forest corporate GIS data themes (e.g., roads, streams, lakes),
the new collar themes were reprojected. Once the export position format
of the GPS_2000 Host software was understood, this relatively straightforward
export process was completed and field maps produced for grazing use correlation
within a day.
|