Survey & Geographic Information Systems (GIS)
Geographic Information System Surveys
GIS Survey Recent Example
Pipeline Route Design Using LiDAR
To investigate by desktop survey the route for a water pipeline to supply the proposed Rig Site with the least terrain resistance.
Using ArcGis and the supplied 1m LiDar Dem to produce a preferred route from the water source to the Rig Site. The requirements for the designated route was for a 10m wide corridor avoiding side slopes, rapid changes in elevation, unstable ground and to keep the route as direct as possible. Helipads to be constructed 1.5 – 2 km apart depending on terrain severity. A pipe staging area also needs to be constructed approximately half way along the route. to be constructed 1.5 – 2 km apart depending on terrain severity. A pipe staging area is also needs to be constructed approximately half way along the route.
The data to calculate the route has been derived from the 1m LiDar supplied and will need to be ground truth and field verified prior to the commencement of line clearing and construction. The terrain along the pipeline route is mainly moderate to severe limestone Karst country. From the rig site the first 500 – 800m is severe terrain through limestone with limited access routes. At the 800m mark the terrain descends moderately over moderate to severe limestone to reach the base of the Donaldson Range. The terrain ascends steeply for approximately a vertical distance of 270m over a horizontal distance of 750m distance. This particular area is the most challenging of the route with very limited access routes. At the top of the range the terrain steeply to moderately descends over severe to moderate limestone to reach the water source staging area. From the staging area the water source is 220m horizontal and 54m vertically lower.
Proposed Pipeline Route.
Utilizing ArcGis 10.4 and the supplied 1m LiDar Dem a preferred route and helipad locations were calculated.
Seismic Survey Line Design using LiDAR.
GU River Dip - Screen shot looking from the East.
The slope model shows that the programmed line traverses over moderate to difficult terrain. There looks to be no reason to deviate outside of the 200m corridor. The corridor is shown as light grey lines in the diagrams
Line Information: Programed HZ dist = 7110m, Calculated Slope Dist = 7607m, Min Elevation 91m and Max Elevation 465m
Areas of interest are circled below
Area 1 looking from the NE shows a vertical cliff of 74m located 1.2km from the start. From the slope model we may have to deviate the line by 50m as shown in blue.
Area 2 looking from the NE, 2.3km from the start shows the line crossing a small river (shown as blue) multiple times. To avoid the crossing we can deviate to the East of up to 70m as shown in red
Area 3 looking from the NE shows a vertical cliff of 30m over 20m located 4.7km from the start. From the model we should be able to navigate the cliff by detouring to the west
Hydrographic Survey Example
Scope of work
- Assess and identify vessel access points across the Kerema bar for landing crafts and alternate tug and barge combinations.
- Assess bar conditions and minimum depths which could be expected during the lowest Astronomical tide/datum (base line).
- Identify the maximum suggested vessel drafts for safe entry through the bar
- Highlight/flag concerns or inherent risks associated with the proposed vessel operations
- Locate, sound, and chart the best water/tracks to enhance safe navigation
- Include waypoints for suggested safe water and courses
- Seek historical information from Bismark/RH on their experience operating over the bar
- Sound/sonar scan and chart the reaches to Kapiri, Epo and Viravi alternate landing, check recorded sonar scans for logs or snags which may be a danger to navigation for vessels running within the estuary/reaches
- Inspect landing points/likely site preparations and investigate options
- Photograph landing areas, bar crossing points and points of interest
- Establish a manual tide station at Epo, collect measurements to verify
- The tide times, range, tidal curves and heights. Correlate with the mathematical tide coefficients for the Kerema bar
- Gain onsite experience to identify additional factors which should positively influence/increase tide heights above the mathematical Astronomical coefficients base line used for the survey
- Positive influences, Climate, Weather, SE/NW trades, Swell, flooding, monsoon and atmospheric pressure
Equipment DescriptionFundamental information required/sounder error
- Accurate GPS positon in WGS84 with time stamp>
- Water depth under the transducer recorded at 5 second intervals with time stamp
- Ability to apply tide coefficient data offsets to each time stamped sounding point
- NOTE: Transducer depths were set at 0.00M, the transducer draft at displacement zero speed was 0.12M, at 7.0 knots 0.06M No offset was applied; therefore all soundings taken have a small inherent margin
- Individual spot soundings inside the bar are affected by wave action. Sounders will record slight error dependent on the swell and wave height, the error is minimal and cancels with the peaks and troughs over time
- Wave/swell action with 0.5 to 1.5M rise and fall on the bar also introduces depth error, on this basis, we increased frequency of lines running parallel to the swell/break to reduce/average out the error.
- 2 x 23ft 60Hp modified Yamaha boats - Latest Lowrance HDS Gen 3 plotters 200KHZ/400KHZ sonar echo sounders with Structure scan (1 x complete back up unit for redundancy)
- NOTE: Transducer offsets were left at 0.00M for the all depths
- Transducer parameters were also set on “saltwater” with salinity and temperature change influence considered negligible in the shallow depths
- Units have inbuilt GPS, below is an early independent test, showing the differences in accuracy between standard positioning and when DGPS/Base Station corrections are applied to earlier Gen 1 units
- PC mapping system to allow processing of collected data, applying tide offsets for each recorded sounding for the duration of the project
- Off the shelf components and software to enable the information produced/generated to be user friendly and easily shared, using readily available services such as Google Earth for dissemination or permit files to be converted in GIS programs