Lecture 3 16/01/2017 (Part A) Flashcards
In-situ data collection, what is it, give examples.
Data collection (i.e., coordinates, elevations, information etc.) completed directly within an area of study (e.g., census date collection, surveying, etc.)
Who launched the first NAVSTAR and when?
1960 US DND launches first ever NAVSTAR
__-__ satellites in view of GPS at any one time, more is better
4 - 12
What type of clock do GPS satellites utilize?
an atomic clock
What is a GPS correction facility?
A control point that helps to make GPS signals more accurate.
provide an example of “in-situ” data collection
surveying
What are the components of surveying equipment?
(Total station) theodolite, stadia rod
What is a Smart Station?
Total station that uses GPS rather than monuments to determine heights AMSL
Census
An official count or survey of an entire population (complete enumeration), capturing select data about individuals within that population.
Sampling
A sample is a select portion of a data set chosen to represent the entire data set (partial enumeration).
What happened in 2011 to the census?
Went from a long form census to a short form census.
What are the 3 segments of a GPS (Global Positioning System)?
1) space segment (i.e., satellites)
2) control (points) segment (e.g., the CG station Alice described to correct measurements to make them more accurate than otherwise)
3) user segment (i.e., the person with the handheld device)
What do all satellites have to account for relativity?
An atomic clock
Orbit at _______ km; 1
revolution per ___ hours
- 20,000 KMs
2. 12 hours
What are the 3 pieces of information a GPS uses to determine position?
- Position (latitude and longitude)
- Velocity
- Time.
What are sources of error for a GPS?
- Sat. clock (sat. is moving quick, smallest error = chaos theory)
- Ephemeris data (sat. current and predicted location, timing and “health”).
- Atmospheric (layers of the atmosphere skewing the signal)
- Receiver Error
- Selective availability (availability of sats.)
What 3 items comprise a total station?
- An electronic theodolite (transit);
- An electronic distance measuring device (EDM); and
- Software running on an external computer, such as a laptop or data collector.
Smart Station
A total station that uses GPS, no laser required.
What is digitizing in GIS?
Digitizing in GIS is:
- The process of converting geographic data either from
- a hardcopy or a scanned image into
- vector data by
- tracing the features.
- During the digitzing process, features from the traced map or image are captured as coordinates in
- either point, line, or polygon format.
What are the 3 Positional Errors with Manual Digitizing
- Map: distorted scale, grainy resolution, poor quality, etc.
- Process: Incorrect translation of control points
- User: Shaky hands, inexperience.
