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
	BG-Map Support

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
BG-Map Support

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:
 		       http://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