Surveying Principles & Spatial Analysis Flashcards

Under the NSSDA, if horizontal error is equal in x and y, how is horizontal accuracy at the 95% confidence level computed from RMSEr?

Answer: 1.7308 x RMSEr

NSSDA horizontal accuracy at 95% confidence equals 1.7308 x RMSEr when RMSEx equals RMSEy.

Under the ASPRS Positional Accuracy Standards, Non-vegetated Vertical Accuracy (NVA) at the 95% confidence level is computed as:

Answer: 1.96 x RMSEz

NVA assumes normally distributed errors, so 95% accuracy equals 1.96 x RMSEz.

In Inverse Distance Weighting (IDW) interpolation, what happens when the power parameter is increased?

Answer: Nearby points gain more influence relative to distant points

A higher power makes weights decay faster with distance, emphasizing the nearest samples.

Which interpolation method uses a semivariogram to model spatial autocorrelation and provides prediction error estimates?

Answer: Kriging

Kriging fits a semivariogram model and produces both predictions and kriging variance.

What is the minimum number of control points needed to solve a 2D affine transformation?

Answer: 3

A 2D affine transformation has six parameters, and each control point provides two equations.

Which parameters define a 2D conformal (Helmert) coordinate transformation?

Answer: One scale, one rotation, two translations

The 2D conformal transformation uses four parameters and preserves shape by applying a uniform scale.

On a DEM, the elevation rises 15 m over a horizontal distance of 300 m. What is the percent slope?

Answer: 5%

Percent slope is (rise / run) x 100 = (15 / 300) x 100 = 5%.