survey grades

[reeffish1073]

what defines the survey grades, for maping?

thanks
john

[Jeff Bartlett]

these are very rarely used in the US. most cartographers, and the American caving community as a whole, prefer that the instruments be listed: "Suunto and Fiberglass Tape", for example. however, i have seen references to survey grades in US documents - the TN cave survey website specifies that new maps submitted for publication be at least Grade 5.

they're common overseas. from http://bcra.org.uk/surveying/index.html :

Table 1: BCRA gradings for a cave line survey

Grade 1 - Sketch of low accuracy where no measurements have been made .
Grade 2 (use only if necessary, see note 7) - May be used, if necessary, to describe a sketch that is intermediate in accuracy between Grade 1 & 3
Grade 3 - A rough magnetic survey. Horizontal & vertical angles measured to ±2.5º; distances measured to ±50 cm; station position error less than 50cm.
Grade 4 (use only if necessary, see note 7) - May be used, if necessary, to describe a survey that fails to attain all the requirements of Grade 5 but is more accurate than a Grade 3 survey.
Grade 5 - A Magnetic survey. Horizontal and vertical angles measured to ±1º; distances should be observed and recorded to the nearest centimetre and station positions identified to less than 10cm.
Grade 6 - A magnetic survey that is more accurate than grade 5, (see note 5).
Grade X - A survey that is based primarily on the use of a theodolite or total station instead of a compass, (see notes 6 and 10 below).

[Caverdale]

they're common overseas. from http://bcra.org.uk/surveying/index.html:

Jeff -

You need to edit this URL to remove the colon at the end.

[Jeff Bartlett]

You need to edit this URL to remove the colon at the end.

oops! thanks for the heads up

[Bob Thrun]

what defines the survey grades, for maping?

thanks
john

The short answer to your question is http://www.bcra.org.uk/surveying/index.html

There have been several grading systems. The British grades were introduced in 1950. They were revised in 1966, 1976, and 2002. The Australian Speleological Federation has it own variant.

The BCRA Grades are defined in terms of measurement accuracy, but there is never any effort to determine if the measurement accuracies meet the standard. A Compass, Tape, and Clinometer (change the order if you want) survey is always called Grade 5. Why not just use Plain English and call it a Compass, Tape, and Clinometer survey? I found that no survey actually meets the Grade 5 standard. All the claimed Grade 5 surveys are actually Grade 4 or 3. You could be liberal with the standard and say the Grade should be based on the instruments used and the hoped-for accuracy, which is the actual practice. But then why not just state what was used? There is enough room on the map. I wrote an article criticizing some Grade 5 claims and going into more detail in Compass Points 31. See http://www.chaos.org.uk/survex/cp/

There are also Detail Grades. The definitions are oddly worded. They are based on how and where details were measured in the cave. They are not based on how much detail was measured or how much detail is shown on the map.

I regard Survey Grades as a failed attempt to be more scientific. It is better to just say how the survey was done.