Week 6: Techniques Flashcards
(81 cards)
1
Q
Surveyors need continually to evaluate choices of methods available for
A
Positioning and heighting surveys
2
Q
Based on the requirements/specifications of each task the surveyor must balance:
A
- The efficiency of a method/technology with respect to time and the associated logistics
- The quality standards to be met and the checks required to ensure the quality standards have been met
- The capital and operational costs involved including the longer term financial impacts (on their businesses and their clients
3
Q
Four surveying principles
A
- We need to ensure reliability of procedures
- ability to detect errors (and whether these can be detected immediately or only back in office
- confidence that results are correct - Need for checks at all stages
- i.e redundant measurements - Need to understand different types of error
- Need to maintain integrity
- Both high moral principles and professional standards:
- Field work, field notes, responsibility to client and profession
4
Q
Precision definition
A
A measure of the repeatability of a set of measurements
5
Q
Precision can be gauged if you
A
Make redundant measurements, compute the mean and the standard deviation
6
Q
Precision assumes that
A
All gross and systematic errors (measurement biases) have been removed
7
Q
Least squares adjustment
A
The sum of the squares of the residuals is a minimum, which may generate error ellipses
8
Q
Precision contains a confidence region that
A
(e.g) 95% of the time includes the point representing the true value
9
Q
Accuracy definition
A
A measure of how close a set of measurements are to the true value
10
Q
Accuracy depends on five criteria
A
- Whethere there are systematic errors present
- The type of equipment (least count: e.g a 1”, 20” or 1’ total station)
- The method used including a suitable reduction model and observing procedure (for instance, whether you correct for twiat of the tripod over time)
- Whether independent checks are made (e.g a double tie)
- If instruments are calibrated regularly
11
Q
Best way to reduce gross errors/blunders in precision and accuracy
A
Incorporate redundancy (checks)
12
Q
Three important surveying principles
A
- Work from the whole to the part
- e.g compute and adjust a main traverse then break this down to subsidary loops - Orientate on a long line, then fix a short line
- not the other way around
- The practical effect of a large observing error on a short orientation will “blow up” into a large error in distant observations from that set-up
- Observation errors on the short line will propagate firther along the traverse - When doing a transformation
- Use control points bracketing the survey area
- Not concentrated in a small portion of it
13
Q
Total stations deal what types of measurements
A
Angle and distance measurements
14
Q
Total stations contain in built software for
A
Survey control, calculations (COGO), communications and data management
15
Q
Total station features:
A
- Lightweight, fairly robust and reasonably water resistant
- Communications ports
- Alpha numeric keypad on screen
- Adjustable illumination LCD display - 1 or 2 screens
16
Q
The different grades of total stations
A
- Construction grade
- General surveying
- Hi-spec surveying
- Motorised and/or robotic
17
Q
Features of different graded total stations
A
- Illuminated reticule for dark observing conditions
- Power supply: battery types, recharging rates, main battery and external plug-in power
18
Q
TS varying instrument H angle accuracies
A
1” 2” 3” 5” 7” 10” 20” +
19
Q
TS cadastral accuracy typically
A
< 7” or better
20
Q
TS angle measurement: set any H bearing of
A
Zero set
21
Q
TS horizontal readings are done to the
A
Left or right
22
Q
TS vertical readings are done to
A
Zenith angles, vertical angles or percentage
23
Q
TS take a set of angle observations and show
A
Mean and standard deviation
24
Q
TS when doing angle measurements, we must adjust out any
A
Horizontal or vertical collimation error
25
TS angle measuremetns can automatically sense and correct for any
Dislevelment in either one or two axes
26
TS angle settings important to know
1. Units and terms available - FL, FR, HL, HR, F1, F2
2. Collimation tests - check by retesting after altering
3. Precision vs display. E.g Topcon 3B - set either 5" or 1" display but +-3" se
27
TS are single and dual axis compensators the same as H or V collimation error
No
28
TS single and dual axis compensators occur when
Vertical axis does not perfectly coincide with zenith (think of a levels compensator)
29
TS single and dual axis compensators will result in
Differences in H and V angle readings
30
TS compensators use either a liquid, pendulum and/or an electronic sensor to find
The zenith and then correct the V (single axis) and possibly the V and H (dual axis) angular readings
31
TS compensators will correct up to
03' of arc disturbance
32
TS compensators are especially important for
Steep angled work - e.g construction
33
TS distance measurements comparison methods
Pulsed or Phase
34
TS distance measurements to single ____ and to triple prisms ____
1000m to single and 2500m to triple prisms (also depends on atmospheric conditions)
35
TS distance measurment modes
Precise, tracking, rapid, average 2-10 (shows std dev), etc
36
TS can apply what types of corrections
Atmospheric (ppm), calibration, C+R and height above ellipsoid corrections
37
TS precision
Easily better than +- 3mm + 3ppm
38
TS reflectorless distance measurements components
1. Phase or pulsed type
2. 100m - 100m in length
3. Depends on: surface reflectance (color), angle of incidence, light conditions
4. Handy for inaccessible sites and structures without targets - unhappy neighbours, bridges, dams, unstable rock walls, etc
39
TS distance settings - must watch out for
Distance reductions and corrections - must know what reductions are being done before a raw distance is displayed
40
Types of distance reductions
1. AC, IC, PC
2. Slope
3. C + R
4. PPMS
41
TS software can be described as ____ to use
Easy (now often menu driven)
42
TS the different functions available in recording and processing
1. REM: remote elevation measurements
2. Resections: 2D or 3D
3. Setting out: 3D
4. MLM: missing line measurements
5. Areas: of any sized polygon
6. Coordinates can be relative or absolute
Important to know what is available and the limitations
43
TS characteristics or motorised TS
1. Automatic tracking of prism using automatic tracking recognition (ATR)
2. H and V servo motor inside TS
3. Automatic search routine
4. Faster and more accurate pointing
5. Operate day and night - in low light conditions
6. Ideal for setting out in open surveying settings i.e often found in engineering surveying
44
TS characteristics of robotic TS
1. Operate TS from the prism. Brains are where important decisions are made. Prism contains keypad to enter descriptions
2. Radio link between prism and instrument
3. 1 person operation possible
4. Uses a 360 prism
45
Error sources for modern TS
Same as normal instruments, in addition to:
1. ATR collimation
2. Laser pointer collimation
3. Reflectorless - unintentional reflections
46
TS how to check/compensate for error sources
1. Two face observations
2. Routine work - full calibration of every instrument should be carried on a regular systematic basis
47
TS power supplies - types of rechargeable batteries
1. NI Mh - most common and best capacity
2. Ni Cad - can handle more charges than Ni MH but will develop a memory
3. Li ion - easy to charg, 1/2 capacity of above, but no memory effects
48
TS three in field developments
1. Full field processing on TS and/or computer notebooks
2. Standard components - Windows, PC cards, real time cellphone transmissions of field data, bluetooth
3. TS incorporating of additional equipment - GPS, scanner, camera, etc
49
Functions of data recorders (DR)
1. Storage of data observed with TS (and GNSS) and transmission to computer
2. Check and reduce data
3. Perform field calculations
4. Essential element of field to finish process
50
Types of data recorders (DR)
1. Customized data recorder - SDR31, TSCe (GPS), Carlson DR - older
2. Portable computer - phone, tablet or laptop
3. Memory cards - insert card into TS
4. On board data recorder - built into TS, hookup cable to TS to up/download coordinates/observations
51
Components of data recorder hardware
1. Compact, portable, weather protection
2. Memory for software and data - may be replace/upgraded
3. Interface required - cable, infrared, bluetooth (bluetooth eliminates main problem with DRs
4. Power sources - batteries, problems with Ni Cads (memory)
52
Components of data recorder (DR) software
1. Basic uses - Topo, traverse
2. Advanced uses - Resections, intersections, line-offset, collimation checks, set out, area, etc
3. Basic reductions - HD, coordinate NEH (or NEZ)
4. Advanced reductions - remote elevation measurements (REM), eccentrics, rotations, transforamtions, missing lines, line offset, etc
5. Time stamp - good cost analysis for biling
6. User defined functions and programs
53
Thirteen advantages of TS/DR combo
1. Fully automated field to finish possible - recording, processing and output of final plan - not fully realised without full combination of features such as feature coding
2. H and V angle compensation - make sure not being done twice
3. Productivity - Quick and easy observations
4. Uniform style of FNs
5. Simple functions - e.g Horiz 0 degree set
6. Increased accuracy
7. Reduced human errors - reading and recording observations: transposing, transcribing no's
8. Checks on data made easily - still major required
9. Prompts for data - no forgetting HI or HT
10. Single face observations (with precautions)
- Assuming corrections to collimation were made
- Assumes collimation does not change WRT time
11. Collects more type of data - provides redundancy and does so automatically
12. Very versatile if preprogrammed
- excellent in expected job situations
- experience valuable in these situations
13. Competitive/business requirement - required for some types of work of for certain clients or some contracts
54
10 issures with TS/DR combo - Big potential 'black box' problem
1. Possible loss of contact with collection process
- are observations reasonable
- are gross and systematic errors noticed and dealt with, ex's a loss of orientation or going off level
2. What corrections are being applied
- Need to know TS and DR settings - record all in FN's (still need some form of FNs)
- Reduction or calc formulas may not be known, read the manual, i.e k value in C and R reductions
- Are they raw measurements, or are reductions being made before you see the data, ie HI and HT being applied already
3. Potential for total data loss - electronic, magnetic, accidental erasure/deletion
4. Component vulnerability - cables, batteries, connections, ports, software, etc
5. Reliant on continual integrity of hardware and software upgrades
6. Unexpected situations - need to know TS well to be adaptable
7. FN diagrams and photos vitally important and necessary
- Ties survey data into a general picture of survey
8. Communication parameters to upload/download
9. Compatibility with office survey software - interfaces, cables, ports, point type - .asc, .cr5, .crd, etc
10. Data storage capability
55
Data management - feature codes definition
A set of codes that allow spatial data to be associated with non-spatial data for the correct interpretation/display of the spatial data
56
Five characteristics of feature codes
1. Used at the time the field data is collected
2. Not simply descriptive, used in post processing
3. Links observations to attributes in FC library
4. Allows adding attributes to a position fix
5. The 'key component' of a field to finish process
57
Examples of feature codes
1. Points - i.e a tree, spot height, fence post
2. Lines - i.e a fence, building (the order of FC's is vital)
3. Commands - i.e closes line (will be label as a command function
58
Combos of feature codes can
Join various point and line features for the same position
59
FC types
1. Point codes e.g TREE, SH
2. Control codes e.g JPT, CLOSERECT
3. Control code parameters e.g SIZE 15,
60
Point codes relate to
Observed position
61
Control codes control
The implementation of the point codes, more typically the linework
62
Control code parameters are
Additional information used typically for plotting
63
The FC library contains a collection of FCs for
1. Different, specific tasks - engineering, topo, industrial, general tasks
2. All definition of all FCs are found here - descriptions, codes, processing features, CAD use - can easily be added to as needed
64
FC library consists of
1. Symbol library
2. Data dictionary
65
Symbol library is
A collection of symbol names and details how each symbol is gnerated
66
Data dictionary is
A collection of FCs preloaded in the DR for a survey job (multiple dictionaries)
- can be uploaded from a computer or created in the field as required
- speeds up entry and ensures accuracy of your survey job
67
FC applications
Allows collection of intelligent survey data, not simply points with labels
68
Put in the work in the field =
Improve efficiency in office
69
How to apply FC in the field for points
Generate correct symbol with size and color, contours, etc
70
How to apply FC in the field for lines
Join points intelligently, specifies the type of line (straights, arcs, curves) and incorporate breaklines into topo survey
71
How to apply Fc in the field for commands
Form closed figures with descriptors attached, omit contours from area i.e building or pond
72
Data collection process
1. Set up job
2. Station details
3. Observations
4. General practice
5. Checks
73
What is involved in setting up the job
1. Job ID - important to use sensible name
2. Check through job parameters
3. Check through instrument details - IC, PC, C and R, PPms, Hi and HT (only done once)
4. Add notes - personnel, weather, location, notable features
74
What is involved in station details
1. Set up point and backsight ID, codes, coordinates
2. Height of instrument - measured and checked x2
3. T and P - if unknown use 15 degrees C, 1013mb (refractive index of air, standard conditions)
75
What is involved in observations
1. Choice of direction only, or dist and direction
2. Can change or use defaults for pt. ID, code, HT - dont forget to change back
3. Offsets may also need to be used, i.e to centre of tree
76
What is involved in general practice
1. TS collimation CK to prove 1 face obs
2. FN's - record: who, what, where, when, equip s/ns, job name, date, weather, any unique FCs used, include field diagram
3. Tape complex buildings pickup up several corners to build from and provides measurement check
4. keep track of field point numbers in FNs
5. C and R affects long line observations
6. Topo - pick up features, changes of grade, spot heights and use and label breaklines
7. Collect, save and store raw data rather than simply coordinates. Allows you to go back in the future if something not set properly and reduce raw data again
77
What is involved in checks
1. Do plenty of them: very important
2. Do checks methodically and systematically
3. Check backsight often
4. Fix same point from more than 1 setup, ie. post, bldg corner, anything unique and confirm coords from each setup
5. Fix to a known point if possible - N E plus H
78
Data processing process
1. Download options
2. Transfer file to database
3. Process feature codes
4. Plot survey and check
79
What is involved in download options
1. Usually (for us) to a TBC or 12D survey job
2. Select required format
3. Hold on a memory stick as a transferable file
4. Use excellent backup procedures to keep long term track of all data
- File maintanance: raw data storage vs processed data
80
What is involved in transfering file to database
1. Might be automatic (TGO)
2. Produces coordinates and heights
3. Many calcs and reductions are performed
- know what is happening to data in reduction process
- carry out initial checks such as duplicate no's, position fixed twice, checks to known points
- editing available
81
What is involved in process feature codes
1. Processing checks feature codes against designated feature code library
2. If problem with existing FCs ability to go back to DC file and edit notes to allow code processing to continue
3. Can also go to library and add/edit codes to reprocess full raw file
