BG-Map Surveying Tip
Questions and Answers Involving Construction and Installation of Survey Markers
Updated 2/26/1999
This document contains an e-mail message thread regarding methods of constructing and installing ground markers (monuments) for use in surveying plant locations in a botanical garden or arboretum.
Question:
FROM: Mark Glicksman DATE: 2/11/1999 RE: Surveying Markers
I would like to get a sense of what different gardens are using as surveying markers - fixed monuments in the ground that can be used for surveying and mapping the locations of plants and other objects.
Some factors to consider are durability, immovability, and ease of location over time as markers become buried under grass and mulch. Also, how do you protect markers in paved surfaces during repaving?
Please let me know what has worked for you as well as what has not worked and why.
Reply 1:
Mark,
As you know, we use round brass markers that are set in 2" galvanized pipe
and these are set in concrete on a surveyed 100 foot grid throughout the
garden. When in garden plantings, these markers stick up about a foot or so
and the pipe is painted a dull green. It is surprising how they melt into
the background. Since they are installed in a grid pattern, it is
relatively easy to locate them, even if they happen to be at the base of a
plant, etc. When the markers end up in asphalt, concrete, decomposed
granite pathways, etc. the brass markers have been set directly in
concrete, flush with the finished surface grade of the surrounding
material. When we resurfaced the decomposed granite paths this last summer,
a number of the markers were initially covered, but they were all uncovered
by the gardeners and are not in holes. We have not yet resurfaced any
asphalt where the markers are located.
The only major problem that we have encountered with the "permanent"
markers is when a major renovation or reworking of an area happens. The
marker typically is removed during (or before) the tractor work is done,
and we have to have the point resurveyed and the marker reinstalled. Staff
does not want the responsibility of placing these fixed reference points,
so we need to bring back the engineering company surveyor (expensive!).
The other problem, and this is regularly encountered, is that all of the
plants that need to be mapped can not be mapped from these fixed grid
points. Numerous other reference points must be mapped and this takes quite
a bit of time.
Bart O'Brien
Rancho Santa Ana Botanic Garden.
Reply 2:
Mark asked: > >>I would like to get a sense of what different gardens are using as > surveying markers - fixed monuments in the ground that can be used for > surveying and mapping the locations of plants and other objects. *** Hi Mark and all, *** What we are doing here at Montgomery has been a long learning process... and still we have not perfected it. Currently, we have a professional survey company come in and place *permanent markers* on the property each year. These markers are cement markers with a round metal disk embedded. Their sizes are approximately 12 inches round. *** Now for semi-permanent markers, we have truly tried many different items. We of course must hop-scotch from the permanent markers around the property.. this is where the semi-permanent markers come in. Our experiences range from rebar with bright colored flags on them or painted with a bright florescent paint... to 8" nails with a brightly colored stake chaser (or whiskers) attached to them... to colored flags on wires... to what we are using now: an 8" nail (bright stake chaser attached) cemented into a 2" pvc pipe about 10" long. And this is very difficult to pound down into limestone rock here in south Florida! > Some factors to consider are durability, immovability, and ease of location > over time as markers become buried under grass and mulch. Also, how do you > protect markers in paved surfaces during repaving? *** We do our best *not* to place markers in paved surfaces. Since we are private non-profit and do not have the high traffic from the public, we have very few paved paths. *** Interested in reading what others do. Thank you, Sue Katz ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Sue Katz Montgomery Botanical Center Collections Supervisor 11901 Old Cutler Road 305.667.3800 x15 (voice) Miami, Florida USA 33156-4242 305.661.5984 (fax)
Reply 3:
RE: RE: Surveying Markers
Mark - how are you?
At Strybing, the reference points we use most are the irrigation
heads we call quick-couplers. They were surveyed in when the ground
plans were initially digitized. Other common markers are large nails
and washers in asphalt paths. We have not had any repaving since the
mapping began, so that issue has not been addressed. We also use
corners of signs or benches, and rarely, large trees. Hope this helps.
Best regards,
Bian Tan
Strybing Arboretum
Reply 4:
Mark,
Holden's survey markers are concrete with rebar. They measure (inches)
4 x 5 x 26, with 4 being at the top. For points that have been
established by a licensed surveyor, there is also a 2" aluminum cap on
top in which a mark is embedded and coordinates North and East are
stamped. Note: surveyors list north first, while AutoCAD lists east
first - a built in conflict.
In gravel work roads and paths of limestone screenings, rebar with a 2"
square cap welded to the top is embedded to grade. These markers are
also being used in our Rhododendron Garden beds and close to large trees
to minimize disturbance caused by installing concrete markers.
No markers of any kind are used on paved surfaces. (We who have lived
in Boston know better than to stand still in such places.)
Ethan Johnson
Holden Arboretum
Reply 5:
Mark, (and others),
We have taken a slightly different approach here at the
Zoo. Because we have so many paths and well delineated beds, along with
numerous "permanent" structures (even if a building is constructed for a
"temporary" exhibit, we know it will outlast any of us here), we have
sufficient landmarks to locate and map our plants pretty accurately. We
simply take a hardcopy map out in the field and "eyeball" in the
location of a plant (or other object). Our mapping is done with
MicroStation (a CAD program that links to our records databases) so it
is very easy to move or adjust a plant's location if later
field-checking determines it necessary. When initiating the mapping
program a (few) years ago, we considered several alternatives, including
the traditional use of a survey team setting permanent benchmarks around
grounds on a grid. In that these are usually placed on a 100 or even 50
foot spacing, we felt we already had an even higher density of landmarks
to use for locating plants (there are a couple of areas that are
exceptions but not many) and decided to save the considerable expense of
hiring a survey team. I believe our methods have worked well for us but
realize without the rather extensive network of paths, etc. this method
would not work. The only drawback to our method is the lack of ability
to describe, without a "picture", the exact location of a plant.
Realizing this may not apply to many (but hoping it may
help some),
David G. Bauman
Collections Botanist/Head Gardener
Indianapolis Zoo
Indianapolis, IN
Reply 6:
University of Nebraska - Lincoln set permanent monuments on campus about 5
years ago. We started with auguring a 14" diameter hole approximately 3'-0"
deep. In the center of this hole we pushed a 7'-0" long, 1" diameter rebar in
the ground so that the top of the rebar was just below grade. Next we placed a
6" diameter by 2'-6" long PVC pipe around the rebar, centering the rebar inside
the pipe, then filling sand around the outside of the PVC pipe to hold the pipe
in place. We placed the sand in the hole outside the pipe to within a foot of
top of grade. We purchased rebar caps, which are just little caps that fit on
the end of the rebar and have an x marked on the top to mark the point, and
metal lids that fit on the 6" PVC pipe. Once the lid is placed on the PVC, then
a concrete collar is poured in the remaining foot around the outside of the
pipe.
The 7 foot long rebar is below the frost line enough that it isn't affected by
heave and the 6" PVC pipe holds the soil away from the rebar to keep any lateral
movement away from the
rebar. The concrete collar holds everything in place and protects the monument
when driven over.
We have very good success with this system on campus. I hope that this
description was clear enough to follow. If not or you are interested in more
information I can be reached at 1-402-472-9138.
Kevin Herr
Manager Landscape Architectural Services
UNL Botanical Garden and Arboretum
Reply 7:
After reading the responses to surveying markers, three questions come to mind:
Is anyone using GPS locating and mapping in their gardens ?
Will GPS make survey(s) -markers obsolete?
Would GPS use save funds spent on engineers' fees?
Steve G.
Reply 8:
>>Is anyone using GPS locating and mapping in their gardens ? The Univeristy of Delaware is using GPS tiied into BG-Map, and Boyce Thompson Arboretum will be coming online soon. >>Will GPS make survey(s) -markers obsolete? >>Would GPS use save funds spent on engineers' fees? Yes and no. Theoretically, once you have a GPS set up, you don't need the markers. But markers are still useful in testing and calibrating a GPS. One thing is certain - you don't need as many markers with a GPS - so the cost in having a surveyor place markers is greatly reduced. Mapping with a GPS is typically s one person operation while mapping by other methods is typically a two person operation. The down side of GPS is reduced accuracy - on the order of 0.5 meters in a typical garden situation - the effects of tree canopies and terrain, which can block GPS signals, and the lack of real time post -processing data in some locations. So, careful analysis is needed to determine if GPS is the best solution for a particular garden. Yours very truly, ------------------------------------------------------------------------- Mark Glicksman BG-Map Botanical Garden Mapping System/GIS
Reply 9:
Mark,
We have two levels of control. We have installed concrete monuments in
several inter-linked, balanced control loops and then we have used 6"
spikes in intermediate locations and for side-shots where control was
needed. We have carried elevations on these points as well, and we leave
them behind for future use.
Our monuments have a magnetic cap as illustrated in the attached drawing
Note to AABGA Listserve - this drawing can be viewed on the Web at:
https://www.bg-map.com/userdata/nybgmark.gif
so location with a metal detector is easy, however, we have been over them
so frequently lately, we can walk to most all of them without difficulty.
Wayne Cahilly
New York Botanical Garden
Reply 10:
Mark, Better late than never, but my E-mail account with U of A has been defunct for quite some time. I am back up, and attempting to catch up on old business. BTA uses a concrete monument formed with old coffee cans or other similar container such as an old planting container, and counter sunk into the ground. A steel washer is anchored in the can of concrete with a screw or flat head bolt of the appropriate size and length to firmly anchor the washer. The coordinates or other pertinent info is punched into the face of the washer. If the marker needs to be visible for work, we sometimes bury a piece of poly tubing along side the maker and paint the tubing either fluorescent orange or to make them less obvious green. The vertical poly tube is flexible and does not present a trip hazard. Hope this response was not too late to be of any use. Thanks and God Bless Ray Dion Boyce Thompson SW Arboretum