A Low-Cost Bathymeter Using Commercial
Off-The-Shelf Components
R. Kremens, J. Faulring, N. Raqueno
Rochester Institute of Technology Center for Imaging
Science
R.I.T
Digital Imaging and Remote Sensing Laboratory
A Low-Cost Bathymeter Using Commercial Off-TheShelf Components
• A Low-Cost Bathymeter Using Commercial Off-The-Shelf Components
• R. Kremens, J. Faulring, N. Raqueno
• Rochester Institute of Technology Center for Imaging Science
• A low cost bathymeter suitable for generation of bottom profile maps of
small to mid-size lakes has been developed. The device uses readily
available commercial components for depth finding (Garmin Fishfinder
100 depth sounder) and positioning (Garmin GPS eTrex) combined with a
custom electronic circuit board that provides data storage and
management. Several data acquisition modes (e.g. manual, timed or
fixed-distance sampling) are available. Eight analog inputs are also
available to measure output from temperature, turbidity, pH or other
sensors. The unit is light, waterproof and self-contained and can be
deployed from canoes or larger powered vessels. Data from the
bathymeter can be automatically downloaded into popular spreadsheet
or GIS applications. Measured bottom profile maps from Coneseus
Lake, NY will be shown, along with estimates on performance accuracy
obtained by comparison with manual soundings.
R.I.T
Digital Imaging and Remote Sensing Laboratory
Depth profiles of small bodies of water are difficult to
obtain at low cost/effort
• Data for small bodies of water is either missing, old or simply
anecdotal
• Hydrodynamic/pollution studies require knowledge of lake
volume and bottom profiles
• Water levels may be affected by seasonal and periodic events
(runoff and sedimentation) so frequent re-measurement may be
required
• Even on large bodies of water (Great Lakes) near-shore data is
often missing or inaccurate to shoaling, bottom movement, old
data
• Design goal: provide a low cost ( < $500) device capable of semiautomatic depth profiling on small lakes ( to 100 m depth)
R.I.T
Digital Imaging and Remote Sensing Laboratory
We have developed a position
aware data acquisition module
(PADAM)
•
•
The PADAM was developed to acquire
data and provide alarms on the wildland
fire line
The PADAM is a versatile field data
recorder:
– 8 channel, 12 bit A/D
– Precision Thermistor conditioning unit
» +/- 0.2 Co absolute temperature
measurement
– Internal non-volatile memory (64kBytes)
– Radio or local (speaker) voice synthesis
– 1200 bps RTTY (transmit only) or Packet
modem (2-way)
– GPS position detection
– Commercial radio transceiver fully
integrated
– Battery life management
» Low power modes
» Power-down standby
R.I.T
Digital Imaging and Remote Sensing Laboratory
Commercial SONAR hardware added to the PADAM
provides depth profiles
• We use an inexpensive Garmin
Fishfinder 100 to measure depths by
SONAR
• A Garmin GPS eTrex Legend with wide
area augmentation system (WAAS)
provides positional accuracy to about
3 meters
• Both commercial devices
communicate with the PADAM via
serial interface
– The depth finder and GPS use
NMEA 0183 message protocol
R.I.T
Digital Imaging and Remote Sensing Laboratory
A number of other environmental parameters may be
optionally recorded using this instrument
• Eight analog channels can record turbidity, downwelled radiance,
weather parameters (relative humidity, wind direction, speed,
barometric pressure)
– Enhanced data acquisition planned for this season
• We are developing a simple probe to measure pressure (depth)
and temperature for determination of thermocline and other
depth-temperature features
• Precision temperature measurement using YSI thermistor
conditioning unit provides surface temperature (at depth
transducer)
R.I.T
Digital Imaging and Remote Sensing Laboratory
The instrument is self-contained, water tight and can
operate for ~ 3 weeks of ‘data days’ without recharging
• Uses NEMA Type 4 waterproof
fiberglass housing
• Total weight of under 6 pounds
makes the unit suitable for
kayaks, canoes or larger vessels
• Rechargeable gel-cell battery
provides 50-70 hours continuous
data recording
• On-board memory module holds ~
1850 data points
– ~19 hectares at 10 m spatial
resolution
– Suitable for complete map of
small pond
– Increased memory >> larger
surveyed area
R.I.T
Digital Imaging and Remote Sensing Laboratory
The bathymeter operates in both manual and automatic
modes
• The device has several
data collection modes:
– Manual – Records GPS
position and depth on
command from user
– Timed automatic – records
GPS position and depth at
a pre-determined time
interval
Data can be acquired at
1 s intervals (limited by
GPS readout)
– Fixed distance automatic –
records position and depth
after moving a specified
UTM, latitude or longitude
R.I.T
Digital Imaging and Remote Sensing Laboratory
On return to shore, the data is downloaded to a PC
using a simple application
•
Applications developed in MS
Visual Basic allow secure
downloading with data set
description information
•
Direct import into MS Excel or
ArcView GIS application
•
Can optionally download data
to PDA using custom
application
R.I.T
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Longitude
Lattitude Depth (m) Time (Z) Date
-77.7084 42.7961
0.7
1852 20021109
-77.7084 42.7961
0.9
1852 20021109
-77.7085 42.7964
1.6
1855 20021109
-77.7085 42.7964
1.4
1855 20021109
-77.7093 42.7972
13.1
1902 20021109
-77.7093 42.7972
13.2
1902 20021109
-77.7093 42.7972
13.6
1903 20021109
-77.7111 42.7975
19.2
1913 20021109
-77.712
42.798
21.4
1916 20021109
-77.7119
42.798
15.4
1916 20021109
-77.7111 42.7983
19.1
1918 20021109
-77.7099
42.798
20.8
1921 20021109
-77.7098 42.7981
15.8
1921 20021109
-77.7084 42.7975
12.6
1925 20021109
-77.7086
42.796
0.6
1638 20021120
-77.7087 42.7963
1.4
1643 20021120
-77.7086 42.7967
7.1
1647 20021120
-77.7088 42.7969
9.5
1650 20021120
-77.709 42.7966
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1653 20021120
-77.7088 42.7967
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1655 20021120
-77.7092 42.7962
5.4
1659 20021120
-77.7091 42.7962
4.2
1702 20021120
-77.7096 42.7962
8.4
1704 20021120
-77.7098 42.7962
8.8
1704 20021120
-77.7103 42.7961
9.1
1706 20021120
-77.7109 42.7959
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1710 20021120
-77.7105 42.7959
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1711 20021120
-77.7101 42.7959
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1713 20021120
-77.7099 42.7957
1.5
1716 20021120
-77.7098 42.7957
1
1718 20021120
-77.7095 42.7957
1
1719 20021120
-77.7092 42.7956
0.7
1720 20021120
-77.7086
42.796
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1723 20021120
-77.7085 42.7959
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1724 20021120
-77.7083
42.796
0.6
1725 20021120
-77.7082 42.7956
0
1735 20021120
Digital Imaging and Remote Sensing Laboratory
Results: Near-shore bottom profiling of Conesus Lake,
NY
• The unit was deployed
from a canoe paddled
around the shore
• Even though this is a
relatively large lake,
bottom profile is
poorly known
• USDA runoff
investigation requires
accurate knowledge
of volume, bottom
profiles, etc. for
hydrodynamic
calculations
R.I.T
Digital Imaging and Remote Sensing Laboratory
Results: Near-shore bottom profiling of Conesus Lake,
NY (2)
• We obtained high-resolution
profiles of a stream entrance into
the lake
• The unit provided very good
agreement with conventional
(weight sounding) methods
– We believe this device is more
accurate than hand sampling!
•By analyzing the strength of the
SONAR return we can provide
rudimentary and automatic
determination of bottom type
(soft, hard, planted)
R.I.T
Digital Imaging and Remote Sensing Laboratory
The unit was able to provide useful depth profiles in the
study area in an hour using an unpowered vessel
• Study area is a
stream outflow into
the lake
• Using random
position, timed
sampling acquired
about 150 points in
one hour with 0.1 m
resolution
•Bottom map is far
superior to what is
available from
conventional
sources
R.I.T
Digital Imaging and Remote Sensing Laboratory
We will incorporate a number of improvements this
season
• Larger memory (256Kbytes) to allow longer data collection
without data downloading
• Surface water temperature and turbidity using thermistor and IR
scattering cell
• Turbidity at depth using weighted probe (10m?)
• ‘Vertical’ position sensor using two-axis silicon accelerometer to
remove ‘angle effects’ caused by wave action
• Ability to add comments to data recording using PDA
• All this adds complexity and cost – is it worth it?
R.I.T
Digital Imaging and Remote Sensing Laboratory