USGS
Patuxent Home button  
button button button button button button button
button

 

Taking your SET readings
This page provides detailed instructions for reading the SET. All designs of the SET are read in the same manner. The first measurement with the SET is called the "baseline" (or Time Zero) reading.
Step 1 - Choose your directions
Step 2 - Place the instrument on the SET benchmark
Step 3 - Lower the pins to the surface
Step 4 - Read the pins and record the values
Step 5 - Repeat for the other directions
Step 6 - Marker Horizons
 
Jervis Bay NSW, Australia
Jervis Bay, NSW, Australia
Step 1 - Choose your directions -

From a single SET benchmark pipe you will have a choice of 8 directions (red lines in below images) from which to take readings. NOTE: The shallow benchmark platforms usually provide only 4 directions once installed.

We normally take readings at 4 of the 8 possible directions (abcd). Typically, the 4 directions are chosen so they are 90 degrees from each other, although other spatial patterns may be required for a particular site or experiment.

Design
Permanent Platform showing plolt layout annd potential directions for the SET.

Having extra directions is helpful should a problem arise. For example, suppose you step in one of your sampling plots and there is now a deep footprint. You could start another baseline using one of the four remaining directions. Be sure to make a detailed drawing of the site layout so you can find your feldspar and SET plots in the future.
Step 2 - Place instrument on benchmark -

Original SET - Place the two pins on opposite sides of the lower (vertical) portion of the SET firmly in the notches of the insert pipe in the direction you want to sample.

SET on insert pipe
Original SET on insert pipe

Rod SET - Remove the cap from the receiver. Attach the Insert Collar to the receiver. Slide the RSET onto the insert collar pointing in one of your four sampling directions. Clamp the SET to the collar once in place.

 

LEVEL. All SET's have a bubble level on them. Be sure to level
the instrument after placing it on the benchmark.

 

Step 3 - Lower the pins to the surface -

If you are working on a marsh site, mud flat or tidal pond, it's helpful if the surface is dry when taking your readings. If the site is flooded most of the time so that you cannot see the sediment surface when placing the pins, its best to use pins with feet. The feet help pin placement by keeping the pin from "piercing" the sediment. Note that "feet" are mainly used in non-vegetated areas such as mud flats and shallow ponds. They do not work well in vegetated areas.

Pins on sediment surface

The pins are held in place by badge clips. Unclip a pin and lower it until it touches the surface. Place the clip back on the pin to hold it in place. Repeat this for the other 8 pins. Placing the pins on a dry surface is mainly accomplished visually. If the surface is underwater, you may have to place the pins by feel (i.e. resistance).

NOTE: At most marsh sites you have to push the vegetation aside while placing pins. In addition, some sites will undoubtedly have detritus, leaves and other materials on the surface. You will need to make a decision on what to remove and what to leave in place.

We normally move away any materials which are not attached to or incorporated into the sediment. For example, we would push aside dead leaves and twigs which are loose on top of the soil surface. We would NOT remove something like a mussel shell or branch which is buried in the sediment. If a pin rests on an unusual surface, such as a branch or crab hole, make a note in the data book.



Placing Pins RSET
RSET - Blackwater NWR, MD USA

Where's the surface?:

Determining the actual sediment surface can be a subjective call, depending on the environment you are working in.

In general, tidal, saline wetlands (Spartina alterniflora, Juncus roemerianus, mangrove forests) and more mineral sediment sites are straightforward and easier for pin placement. Sites with more organic sediments (fresh and brackish marshes), can be more difficult for pin placement due to the uneven nature of the surface. Shallow ponds or waterways are generally easy since you have the "feet" on the pin and the bottom is relatively uniform.

Regardless of the environment you are working in, it's important that you are consistent from sampling to sampling in how you determine pin placement. Establish a protocol and follow it.

 

Step 4 - Read the nine pins and record the values -

The pins will stick up above the level aluminum plate or arm on the instrument. You will need to measure the distance from the plate or arm to the top of the pin.

What to measure
Reading RSET

Old Oyster Bayou, LA USA
Reading Original SET
Sapelo Island, GA USA

It's important to record any specific information on individual pins. Make a note if a pin falls in a hole, on a mussel shell, on a tree root, etc. Some of these values may not be used in calculations based on this information so it's important to document this as you take the readings.

Below is a sample table showing how we organize our databook (Four directions from a single pipe). Values are in millimeters.

Marsh Site 1 - Pipe 1 - February 14, 2003
Direction
Pos 1
Pos 2
Pos 3

Pos 4

Bearing
NE 40°
SE 130°
SW 220°
NW 310°
Pin 1

121mm

132 122 134

Pin 2

120 129 140 121
Pin 3
120 133 125 119
Pin 4
123 133 122 128
Pin 5
125 132 141 115
Pin 6
119 126 139 149 Shell
Pin 7
128 101 hole 133 119

Pin 8

131 122 126 125
Pin 9
130 121 123 128
SET read by: Jim Lynch, SET ID#=2002-1

Step 5 - Repeat for the other directions -

Don't forget to level the instrument prior to placing the pins at each of the positions.

Reading Original SET
Delta NWR, LA USA

 

Who reads the SET?

We recommend that the same person read the SET from sampling to sampling. This approach will maintain a consistent sampling protocol when taking the readings and minimize sampling errors.

Double Reading the SET:

If you need to switch readers, we recommend that you "double-read" the SET during one of the samplings. For example, suppose SET READER #1 has been reading the data since the project started, but is leaving for a new job. SET READER #2 is going to replace him/her. The best situation would be for both readers to go and sample the site together. READER #1 would take their final set of readings with the SET. Then READER #2 would take a repeat set of readings.

You should also double read if you are switching pins. For example, if you wanted to swap out your pins for longer pins with feet you could double read the sites with the two sets of pins. A final reading with the original pins and a baseline reading with the new pins.

This can make for a lot of work, but it will ensure a smooth transition of data collection.


Step 6 - Marker Horizons:


If you are establishing Marker Horizons you should put them out when you are taking your first SET readings. This way the values from the SET and the marker horizon have the exact same starting date. If the dates vary you could have some problems interpreting the data in the future.

If Marker Horizons are already established and you need to sample them, click here.

 
U.S. Department of the Interior, U.S. Geological Survey,
Patuxent Wildlife Research Center | URL: http://www.pwrc.usgs.gov/
Last Updated: 18 February 2010
Privacy Statement | Disclaimer