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CEG2710 - GNSS THEORY AND PRACTICE Stuart Edwards/Matt King Q1 – double difference component of the question was generally well answered with the double.

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Presentation on theme: "CEG2710 - GNSS THEORY AND PRACTICE Stuart Edwards/Matt King Q1 – double difference component of the question was generally well answered with the double."— Presentation transcript:

1 CEG GNSS THEORY AND PRACTICE Stuart Edwards/Matt King Q1 – double difference component of the question was generally well answered with the double difference solution established commencing with the undifferenced observable and identification of receiver and satellite clock errors as being cancelled. – A large number of answers correctly suggested cancellation of some errors over short baselines, but some did not qualify it is only for short baselines. – The undifferenced observable was poorly described, although students were given the equation many times in class. Only a small number attempted this sub-question so nearly half marks lost.

2 CEG GNSS THEORY AND PRACTICE Stuart Edwards/Matt King Q2 – The description of multipath was generally well handled. Many answers missed an attempt to give the magnitude of code and carrier MP – 0.5-2m and <1/4 wavelength (~0.05m) respectively. – This question was often not attempted. – Generally quite well answered, with answers focusing on site choice. Fewer had choke ring antennas and even fewer data weighting.

3 CEG GNSS THEORY AND PRACTICE Stuart Edwards/Matt King Q3 – This three part question was based around the 3 rd practical in the module where students used network RTK (NRTK) equipment in the field and then prepared an individual write up on the topic of NRTK. As such I would have expected the question to be answered by many and this was the case. – However, overall the question was not answered well at all. The bulk of the marks (15) were given for explaining the theoretical principles of the VRS NOW and SmartNET NRTK systems. It was disappointing to note that students made a significant number of mistakes even though they had previously (and recently) submitted a piece of coursework which required just this, and I had previously fed back to them on this coursework outlining that some needed to revisit the notes. – The question asked for diagrams as appropriate but very few actually provided any diagrams of system data flow etc., which would have saved them much writing and provided clarity at the same time.

4 CEG GNSS THEORY AND PRACTICE Stuart Edwards/Matt King Q4. – Question posed a simple scenario for a static GNSS survey for several points to be established over baselines up to 30 km to be processed to deliver 1-2 cm accuracies in plan. 17 students attempted this question. – The fundamental mistake that many made was in their approach. The aim of the question was to get students to think about what would be required in terms of planning, equipment, data observations, processing and quality analysis. – A report style with appropriate headings would have sufficed in this regard but many chose to write a rambling and unfocussed essay. – However, most students lost marks was due to failure to provide sufficient detail on the areas outlined giving very generic answers only. Some candidates did not read the question e.g. referring to processing baselines over 100 km and using NRTK!

5 CEG GNSS THEORY AND PRACTICE Stuart Edwards/Matt King – Only 7 students attempted this question. – Many seized upon the term CORS and wrote an essay on the OS CORS network which was did not answer the question. – Many answers were again too generic and displayed little actual knowledge of third party products despite using RINEX data and orbit products in practical 02. – Disappointing as students had actually used 3 rd party products and investigated their performance in Practical 2. – It would appear that students are not able to link work done in practicals to the wider theory covered in class. – Overall, a poorly answered question

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