Transcript powerpoint slides

CEG2710 - GNSS THEORY AND PRACTICE
• Q1
Stuart Edwards/Matt King
– 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.
CEG2710 - 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.
CEG2710 - GNSS THEORY AND PRACTICE
• Q3
Stuart Edwards/Matt King
– This three part question was based around the 3rd 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.
•
CEG2710 - 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!
CEG2710 - 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 3rd 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