SurveyorSimstudent guide · the exercises
What each exercise is asking you to do
Eight kinds of assignment ship with SurveyorSim. Your instructor sets the numbers — how many points, how tight the tolerance, what the site looks like — so this page does not quote any of those. What it gives you is the shape of each exercise and the one thing students most often get wrong in it.
Before any of them
true of every exercise- The task panel is the assignment. It carries the objective, the tolerance you are being held to, and a numbered What to do list. Those numbers are your instructor's, not this page's.
- The names are your instructor's too. Marks called BM-A or CTL-1 are what the sim invents when nobody has authored a site. On a site your instructor drew, the marks carry whatever names they typed.
- Kit can be withheld, and nothing on screen says so. If a button you expected — the shot log, the calculator, the data collector — is not there, your instructor took it out of your kit on purpose for this assignment. It is not a broken page, and the sim will not name what is gone. Work with the kit you have.
- On a crew, only the chief hands in. Whatever you type on your own screen stays on your own screen.
- Submit is final, and you are asked to confirm it. If a banner ever says nothing is being saved, stop and tell your instructor — that one is not recoverable.
Differential leveling loop
the one graded from your bookRun a level loop over the benchmarks and close within the order tolerance.
Set the level, read a backsight, walk it forward turning point by turning point, and close. The instrument is an automatic level: its setup is shorter than the total station's — legs and bubble, and the compensator does the rest. No plummet, no instrument height to measure.
- Your allowance is not a fixed number. It grows with the length of the loop you actually walk, and it stops shrinking at one graduation of the rod.
- A loop closes on the benchmark it started from. Some runs instead finish on a different benchmark — that is a link, not a loop. Either way your closing tag goes on the benchmark you finished at, and tagging the one you started from is graded against the wrong published elevation.
- Your page also needs a title line, and the graph page a sketch. Nothing prompts you.
- Set the rod on the point, face the instrument, and set it again if you moved. At each benchmark and turning point, choose Set rod on: the rodman stands on the point and turns to face the level, so the observer reads the rod and not the rodman's back. Any step after that, even one to turn round, takes the rod off the point and the reading is wrong. The ✋ chip then says the rod is off the mark; choose Set rod on again before the observer reads.
Three-wire leveling
The level's reticle has three horizontal wires: the middle one, and a stadia wire above and below it. Reading all three at every sight is three-wire leveling (Ghilani & Wolf, Elementary Surveying, ch. 5, “Three-Wire Leveling”). It catches a misread rod, gives you the mean of three readings instead of one, and measures every sight so you can balance them.
- Read the upper, middle and lower wires — U, M and L — on every backsight and every foresight, each to the hundredth of a foot, or to the millimetre on the metre rod. Have the rod held plumb on its rod level for all three, not waved: a wave finds the minimum on one reading, so three wires on a waved rod are three readings from three different moments, and for careful work, the rod level is the better tool.
- Check before you leave the sight. U − M and M − L should be equal. If they differ by more than two of the units you read to — two hundredths of a foot, or, on the metre rod, two millimetres — read all three again. The field book's own formula page (⋯, ƒx Reference formulas) carries the same check.
- Book five lines in the sight's own column, BS (+) for a backsight and FS (−) for a foresight: the three readings, their sum, and the mean.
- Book the stadia in the STADIA column beside that sight: each half-interval times one hundred, on the middle and lower lines, and their sum — the length of the sight — on the sum line.
- Carry the mean, not the middle wire. Down the ELEV column, the backsight mean added to the elevation gives the HI, the height of the line of sight; the foresight mean taken off the HI gives the next station's elevation.
- Balance every setup. Before you move the level, compare the backsight's stadia with the foresight's and keep the two about equal. That is what the second STADIA column is for: a balanced setup cancels curvature and refraction, and a line of sight that is not quite level.
| STA | BS (+) | STADIA | FS (−) | STADIA | ELEV |
|---|---|---|---|---|---|
| BM-A | 100.000 | ||||
| 5.21 | 3.81 | ||||
| 4.50 | 71 | 3.12 | 69 | +4.503 | |
| 3.80 | 70 | 2.42 | 70 | 104.503 | |
| Σ 13.51 | 141 | Σ 9.35 | 139 | −3.117 | |
| 4.503 | 3.117 | ||||
| TP-1 | 101.386 |
Both checks pass here: the backsight's half-intervals differ by one hundredth of a foot, and so do the foresight's. The setup is balanced, a sight of 141 against one of 139. Tagging is unchanged: the elevation you carried to a turning point is the cell you tag.
The page check
Before you leave the page, check your arithmetic: the backsight means added up, less the foresight means added up, must equal the last elevation less the first. Sum the means, never the whole column. On a three-wire page the BS and FS columns also hold the three readings and their Σ, so the whole column adds up to about seven times the sum of the means. The check is not graded, and it catches arithmetic, not a misread rod. Here is the next setup on the same page.
| STA | BS (+) | STADIA | FS (−) | STADIA | ELEV |
|---|---|---|---|---|---|
| TP-1 | 101.386 | ||||
| 6.02 | 2.87 | ||||
| 5.33 | 69 | 2.17 | 70 | +5.327 | |
| 4.63 | 70 | 1.47 | 70 | 106.713 | |
| Σ 15.98 | 139 | Σ 6.51 | 140 | −2.170 | |
| 5.327 | 2.170 | ||||
| TP-2 | 104.543 |
And the check over both setups:
| Setup | BS mean (+) | FS mean (−) | Running BS stadia | Running FS stadia |
|---|---|---|---|---|
| BM-A to TP-1 | 4.503 | 3.117 | 141 | 139 |
| TP-1 to TP-2 | 5.327 | 2.170 | 280 | 279 |
| Σ of the means | 9.830 | 5.287 |
The page check: 9.830 − 5.287 = 4.543, and the elevations give 104.543 − 100.000 = 4.543, so the arithmetic holds.
Keep the balance running, too. Keep each setup balanced, and keep the running sums of the backsight and foresight stadia close down the page: a long backsight on one setup can be made up on a later one, because it is the page's two totals that have to come out near even (Ghilani & Wolf, ch. 5, “Three-Wire Leveling”). Here the first backsight ran long, the second foresight took some of that back, and the page stands at 280 against 279.
Closed traverse
occupation, not just anglesOccupy the control points, turn the angles, close the loop, and fix each point to the required accuracy.
Set up over each control point in turn, backsight the previous one, turn the angle to the next, and measure the distance. Shoot both faces and mean them — that is what cancels the instrument's collimation and index error, but the collimation only in a direction seen on both faces, so shoot the backsight on both faces too. On a real instrument it is not your only defence: those corrections are determined on site and stored, and repeating the angle on several circle positions beats down what face-meaning leaves behind.
Four things are graded, equally:
- Every control point occupied. The instrument has to stand over each one. Shooting a point from somewhere else is not occupying it.
- The loop closed. Your closing sight back on the start, against the coordinate on its sign, over the length of the loop — the same misclosure you compute yourself. The loop is the chain your coordinates were carried round, so every control point has to be in it.
- Every point in position. Each control point against where it truly is.
- The azimuth closed. Set up on the start again, measure the last control point, then turn and measure the control you first backsighted. The azimuth your angles carried round the loop is checked against the one between the two signs, within K″√N for a loop of N legs. A blundered angle turns the rest of the loop and can hide inside the closure; this is the line that catches it. Hand in without that setup and the angles were never checked, so the work cannot pass: if everything else passes, this line fails.
Your standard is on the task panel, and both the closure and the positions are held to it; it sets the azimuth's K too. The closure and the positions can disagree, and that is a lesson, not an error: a loop can close well and still sit turned or stretched as a whole. The closure is the check you can make standing on the site, and it is the one your instructor will ask about.
Chaining / taping
a foot tape, alwaysChain between the set marks and report each measured horizontal distance.
Take the tape from your kit and measure between the marks, then report each distance in the task panel. On broken ground you will need to break the chain — level the tape in stages rather than dragging it down a slope. Where a rise stands between the two ends, Hold both ends clear lifts both of them over it so the tape can run straight across the top. Sight it on the hand level, which keeps it clear far more often than by eye; either way a drooping end can still bring the tape back down onto the rise, most of all on a long pull with the rise near the lower end, and then it has no reading. If the rise is too high to clear, set a pin at the top and break the chain there.
Feedback on each leg tells you the direction only: within tolerance, too long, too short, or not reported. When the tolerance is a ratio of each leg's length, it names that leg's allowance in feet too. It never tells you by how much you were off, on purpose — that would hand you the answer.
Monument recovery
the shovel is graded tooTurn the record angles and distances from control, then dig to recover the monuments.
You are given record measurements from known control. Turn them, walk out to where the monument should be, and dig. The monument is really under the ground — finding it is the exercise.
- Your digs are counted, and the count is a graded line. Digging a trench across the site is not a strategy.
- Backfilling does not hide a hole. The record of where you dug is kept either way.
On a subdivision, your task panel also hands you the recorded plat. Open the recorded plat shows the plat sheet full screen — zoom with + and −. Below it are the basis of bearings, the published control, and the calls of each lot you are sent to: every lot line as a bearing and a distance in U.S. survey feet, and on a curve its radius, delta and arc length, as the curve table records them.
Stakeout
judged on your worst stakeStake the design points within radial tolerance of their true positions.
The design coordinates are on the task panel, in a section headed Design points. Set up, compute or read off the direction and distance to each, and put a stake in the ground.
Topographic survey
coverage is the exerciseMap the ground inside the marked square: shoot enough well-placed points that a contour map could be drawn from them.
Radiate from published control and shoot the ground — breaks in slope, the tops and bottoms of banks, and enough of the flat between them that a contour could be drawn through your points.
- Coverage is checked cell by cell. A cluster of shots in one corner and a bare patch elsewhere fails, however many shots you took.
- Only shots inside the square count. The corner stakes are the boundary of the job, not decoration.
Plat retracement
three outcomes, all gradedRetrace the record plat from its control: recover the lot corners that stand, re-establish the missing ones and report the disturbed ones.
You are handed the recorded plat of a subdivision and two control points, and sent to the corners of one or more lots. Work out from the calls where each corner should be, go there, and find out what is really in the ground. Each corner is one of three things: found where the record puts it, disturbed — a rod is there, but off its record position — or missing, with nothing in the ground at all.
- Found: dig it up. Leave it as it is, or tie any flagging on it but orange.
- Disturbed: dig it up and tie orange flagging on it. Orange is the report, so orange on a rod that has not moved counts against you.
- Missing: set a new iron rod (Place mark) at the record position. It has to land within the tolerance your panel gives.
Open world
your instructor sets the taskAn open-ended session on a site your instructor has built. The task is not in the sim — it is on their handout, or on notes placed around the site itself. The panel still gives you steps, and they are about finding the task rather than doing it.
- Walk into a note to read it. Notes are placed on the ground and open when you reach them.
- The notes may be in order. On some sites note 2 will not open until you have walked into note 1. If a note seems dead, you have probably skipped one.
- Nobody grades this automatically. Your instructor reads the record and assesses it themselves — so what you leave behind in the field book and the collector is the whole submission.