GPS and Field Data Collection Flashcards
6 cards from real GISP practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 GPS and Field Data Collection flashcards as text
What is the primary purpose of a control point survey in establishing a geodetic network for GIS mapping projects?
Answer: To provide precisely measured reference locations for georeferencing and spatial accuracy
Control point surveys establish accurately positioned reference monuments that serve as the foundation for georeferencing maps, imagery, and other spatial data to a consistent coordinate framework.
When collecting GPS points for a polygon boundary, what field practice minimizes positional error at vertices?
Answer: Averaging multiple position readings (position averaging) at each vertex
Position averaging records multiple GPS readings over a period of time at each vertex and averages them, reducing random errors and improving the accuracy of boundary vertex locations.
Which datum transformation parameter set is required when converting GPS coordinates (WGS84) to NAD83 for use in US federal mapping projects?
Answer: NADCON or HARN grid-based transformation
NADCON (North American Datum Conversion) and HARN (High Accuracy Reference Networks) provide grid-shift files that accurately transform coordinates between WGS84 and NAD83, required for precise federal geospatial work.
In a GIS field data collection workflow, what is the primary advantage of using a geodatabase schema loaded onto a mobile device over collecting raw GPS tracks?
Answer: Attribute data is collected simultaneously with geometry using validated domain fields
A pre-loaded geodatabase schema with coded value domains, default values, and required fields ensures that attribute data is captured accurately alongside geometry during the field collection process.
What is the significance of the PDOP (Position Dilution of Precision) threshold of 6 commonly used in GPS field surveys?
Answer: It is the maximum acceptable geometric dilution before positional accuracy becomes unreliable for most GIS applications
A PDOP of 6 is widely accepted as the upper threshold for acceptable GPS survey conditions — values above 6 indicate poor satellite geometry and degraded positional accuracy that may be unsuitable for precise mapping.
Which technique allows a GIS technician to collect GPS data along a linear feature such as a trail or road centerline?
Answer: Track logging
Track logging continuously records GPS positions at set time or distance intervals as the receiver moves, creating a series of points that define a linear or areal feature's path.