How to book a level run
- Type the RL of your starting benchmark at the top.
- Sight the staff on the benchmark, tap BS, type the reading and press Enter.
- Book every other point you see from that setup as IS. The last point before you move the level is the FS.
- After the move, book the BS on that same point. It goes on the FS line, as a change point does on paper.
- Under Closing, pick the start benchmark or another one to see the misclosure and adjust.
Tap any line to edit, insert or delete. Book an upside-down staff with a minus sign.
Reading the checks
ΣBS − ΣFS = ΣRise − ΣFall = Last RL − First RL. When the three disagree, a reading was booked in the wrong column, and the marked line says which. In the HI method, each HI times the number of sights taken from it, less ΣIS and ΣFS, equals the sum of every RL after the first.
These checks prove the arithmetic only. A misread staff passes them; closing on a known benchmark tests the readings.
Example: a small loop from BM 1
| Point | Reading | Rise (+) or fall (−) | RL |
|---|---|---|---|
| BM 1 | BS 1.425 | 100.000 | |
| A | IS 2.115 | −0.690 | 99.310 |
| B | IS 1.892 | +0.223 | 99.533 |
| CP 1 | FS 2.304 BS 0.987 | −0.412 | 99.121 |
| C | IS 1.543 | −0.556 | 98.565 |
| CP 2 | FS 1.212 BS 2.346 | +0.331 | 98.896 |
| BM 1 | FS 1.238 | +1.108 | 100.004 |
4.758 − 4.754 = 1.662 − 1.658 = 100.004 − 100.000 = 0.004. The loop closes 4 mm high; third order allows 12 mm × √0.191 = 5.2 mm, so it passes. Open this example in the book.
Questions
Is rise and fall or height of instrument better?
Both give the same reduced levels. Rise and fall checks every intermediate sight, so it suits sections and profiles. Height of instrument is quicker by hand with many intermediate sights. You can switch at any time.
How is the allowable misclosure worked out?
Most limits are C mm √K, with K the run length in kilometers. FGCC 1984 gives 12 mm √K for third order and 8, 6, 4 and 3 mm for the higher orders (p. 3-7). A common teaching rule is 5 mm √N, with N the number of setups (Soil Engineering Practical Workbook, p. 17). Pick the one your job sets or type your own C.
How is the misclosure spread over the run?
Equal per setup gives every point seen from setup k the share k/N, with the opposite sign. By distance shares it by the distance leveled up to that setup (WSDOT manual, 10-03.5). An intermediate sight takes the correction of the setup it was read from, and the closing point lands on its known RL.
How do I book three-wire readings?
Turn on three-wire in Book settings and type the upper, middle and lower wire. The book uses their mean, takes the distance as 100 times upper minus lower, and marks a sight whose two intervals differ by more than the limit: 3 mm, the FGCC third-order check (p. 3-7), or 0.010 ft in feet.
What happens if I close the tab or lose signal?
Every keystroke is saved on this phone, even a half-typed reading, so the book comes back after a reload or a closed tab. Once loaded, the page works with no signal. A private window forgets everything when it closes, so export a CSV first.
Sources: FGCC, Standards and Specifications for Geodetic Control Networks (1984), p. 3-7; WSDOT Highway Surveying Manual, chapter 10, pp. 10-2, 10-3 and 10-7; Soil Engineering Practical Workbook (2021), p. 17.