GISP GPS and Field Data Collection 2

Question 1

What is the primary purpose of a control point survey in establishing a geodetic network for GIS mapping projects?

Accepted Answer

To provide precisely measured reference locations for georeferencing and spatial accuracy

Answer

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.

Question 2

When collecting GPS points for a polygon boundary, what field practice minimizes positional error at vertices?

Accepted Answer

Averaging multiple position readings (position averaging) at each vertex

Answer

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.

Question 3

Which datum transformation parameter set is required when converting GPS coordinates (WGS84) to NAD83 for use in US federal mapping projects?

Accepted Answer

NADCON or HARN grid-based transformation

Answer

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.

Question 4

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?

Accepted Answer

Attribute data is collected simultaneously with geometry using validated domain fields

Answer

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.

Question 5

What is the significance of the PDOP (Position Dilution of Precision) threshold of 6 commonly used in GPS field surveys?

Accepted Answer

It is the maximum acceptable geometric dilution before positional accuracy becomes unreliable for most GIS applications

Answer

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.

GISP - Geographic Information Systems Professional Practice Test

GISP - Geographic Information Systems Professional Practice Test

GISP GPS and Field Data Collection 2