Inland Towns Lidar
Inland Towns Lidar was a joint project which required Land Solution Australia to conduct and deliver GNSS (Global Navigation Satellite System)Control Survey requirements in two Stages 3 and 4 encompassing small town regions. Stage 3 incorporated Atkinson Dam, Toogoolawah, Esk, Kilcoy, Dysart, Nebo, Clermont, Moranbah, Richmond, Maxwelton, McKinlay and Kynuna and Stage 4 covered over 67 regional towns of Queensland. This massive project allowed Land Solution Australia to provide detailed reporting concluding that GNSS RTK and static survey methods clearly provided an efficient method for collecting the survey data for this project. Based on the equipment and methodology used for the survey, Land Solution Australia estimate the relative accuracy of the observations to be +/- 0.05m in position and height. Pre planning of the base station positions on known DATUM control marks meant that a high correlation was common for most sites in position and height.
Over an extensive time period between 2011 to 2012 the Inland Towns Lidar project requirements for Stage 3 were to provide survey datum for height/origin and horizontal/origin, static observations survey control, RTK observations and Post Processed Kinematic (PPK) observations and for Stage 4 to provide survey datum for height/origin and horizontal/origin. DATUM Control points supplied by DNRM were used from the Survey Control Data Base (SCDB) for Height and Horizontal Datum/Origin.
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For the Inland Towns Lidar project two different survey methodologies were used to provide the control. Initially towns were planned such to observe DATUM control marks in the locality of each LIDAR site. Heights for each town were AHD, Ausgeiod 09 interpolated. LIDAR test point data was observed by surveying road centrelines throughout the Lidar area and post processing the kinematic survey data. This was undertaken by recording 1 sec epoch data at two base stations, and using a third receiver mounted on the front of a mobile vehicle to record 1 sec epoch data generally along the centreline of each roadway. A vehicle mount clear from obstruction with a general vehicle speed of 40km/h while observing the road centreline was undertaken. Roadways were generally driven in both directions or twice to give redundancy to the survey observations. Following the kinematic survey, the height of the base stations were changed and independent static observations were observed to other approved QEHA10.7 control in the locality. Generally as a minimum, three existing control marks were observed to control the height and position of the data observations. Prior to departure, the field crews then downloaded their data and post processed both the static and kinematic data segments for each town. GLONASS satellites were not used to process kinematic segments but were used for static processing due to limitations with the processing software. Kinematic segments were generally processed for both base stations at 1 sec intervals using a high data integrity filter within the Justin software. This produced two independent data sets and the 1 sec epoch interval. Where insufficient data was fixed after processing, the surveyor re-observed all or part of the kinematic segment for the test point site and again processed the new data until a reasonable coverage of the area was fixed after post processing. This process was repeated for each town.
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Land Solution Australia as instructed for the Inland Towns Lidar project Stage 3 and 4 allowed for 50-100 spot heights to be collected within each external bounding polygon for each town; Horizontal and vertical positioning must be controlled by reference to existing approved permanent survey marks established with GDA94 coordinates and accurate AHD levels suitable to meet the final LiDAR data specified accuracies; Survey techniques used to establish a primary control must achieve a minimum standard of horizontal Class B and vertical Class B or 4th order spirit levelling, in accordance with the Inter- Government Committee for Survey and Mapping Standard and Practices for Control Surveys (SP1) and satisfy the requirements for inclusion of the coordinates into the Queensland Survey Control Database (SCDB); Survey control data used or derived from this contract is required for independent quality assessment, and may be included as part of the State’s survey control infrastructure. It is therefore essential that all primary ground reference (base) stations are permanently marked in accordance with the Survey and Mapping Infrastructure Act 2003; Heights of these primary ground control points and all check surveys must be referenced to the “local” AHD datum as defined above, which is comprised of State survey control marks with accurate AHD heights as defined survey practices according to SP1. GDA94 coordinates must be derived using methods commensurate with the accuracy requirements stated above; All spatial data was supplied in MGA Zone applicable to the site polygon and on AHD using the new AUSgeoid09 system. All LiDAR check point information and other relevant details will be supplied to the Department of National Resources and Mines to include in the National Adjustment and refinement of Ausgeoid.