[Coral-List] Mapping procedure

John McManus jmcmanus at rsmas.miami.edu
Sat Aug 9 13:17:50 EDT 2003

Hi Marianne,

In our work in the Philippines before the advent of GPS, we found that
the best way to make sure you were moving in a straight line was to keep
two poles in view, one behind the other. This was easy going to or from
shore -- we could put painted bamboo poles in in the sand at about 10 m
distance. Sometimes hanging signs on them helped. Out at sea, we
anchored weighted bamboo poles as buoys.

Instead of compasses, we found that it was often easier (especially in
waves) to determine locations via plastic sextants held horizontally to
triangulate off of landmarks and the poles. We had ordered these from a
boating supply company. If you don't have differential GPS units, this
approach may be a useful way to check your locations. However, we also
used the sextants to triangulate locations of boats, rocks etc. at sea
from a distance. We also used a forestry rangefinder for this, but with
less success.  

If you need to know about airborne groundtruthing tools (ultralights,
remote aircraft, etc.) for interpreting remote sensing imagery to make
maps, see:

McManus, J.W., Nañola, C.L., del Norte, A.G.C., Reyes, R.B. Pasamonte,
J.P.N., Armada, N.P., Gomez, E.D. and Aliño, P.M. 1996. Coral reef
fishery sampling methods. Chapter 5. p. 226-270. In: V.F. Gallucci, S.B.
Saila, D.J. Gustafson and B.J. Rothschild (eds) Stock Assessment:
Quantitative Methods and Applications for Small-scale Fisheries. CRC
Lewis Publishers, New York. 527 p.




John W. McManus, PhD
Director, National Center for Caribbean Coral Reef Research (NCORE)
Rosenstiel School of Marine and Atmospheric Sciences (RSMAS)
University of Miami, 4600 Rickenbacker Causeway
Miami, Florida 33149. 
jmcmanus at rsmas.miami.edu 
Tel. (305) 361-4814
Fax (305) 361-4910

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
[mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Marianne
Sent: Thursday, August 07, 2003 5:10 PM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Mapping procedure

Hi fellow listers,

I am looking for anyone who has a good procedure for mapping shallow 
coral reefs using GPS and single-beam sonar.  We are trying to 
roughly map depth profiles of reefs around Samoa.  We have an Eagle 
Seacharter that can record both depth profiles and GPS coordinates.  
We are planning to enter the data into MapInfo.  

It would be a lot easier/cheaper for us if we can do this using 
Polynesian canoes instead of a motor boat.  I tried mounting the 
probe on a canoe and it works but wind and currents can be a problem 
when trying to travel in straight lines...  Any advice from people 
who did similar things would be greatly appreciated! 

Thank you!


Marianne Gilbert
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