What is Remote Sensing????: Aerial Photographs and Landslide Delineation using erMapper and ArcGIS

Labwork for ESC 4511 Environmental Remote Sensing:

Question need to be answered before we start using erMapper:

1. What is rectifying process?

Simple words that explain all is the process of converting/reassign coordinates to pixels from few images into a one common plane. In details, rectification process is a transformation process that used to project 2 or more images onto a image plane/ planimetric image. It’s also part of data projection that bring geometric characteristics of data into conformance with a know coordinate system. Rectification process correct any distortion by transforming the image into standard coordinate system.

2. What is GCP (Ground control point) in rectifying process

GCP are points that greatly influence the accuracy of spatial interpolation of a data. GCP normally are points on a paper or digital map that has known coordinates and is used to transform another dataset. GCP serve the purpose of:

· Digitizing data from from paper maps

· Georeferencing both raster and vector data

· Spatial adjustment operation

In short, GCP stands for location that are identified on the raster dataset and in real-world coordinates

3. What is map projection

Map projection is the process of expressing the 3D surface/ curved surface of the earth into a 2D flat surface of a map. Map projection commonly and are important in creating maps. However, it is not an easy job to project an 3D image onto a 2D surface as distortion happens when doing so. Therefore, a good globe can provide accurate representation of the earth and aid in map projection.

4. 4. What is geodetic datum

Tools used to define the size and size of the earth and the origin and orientation of the coordinate systems used to map the earth

5. 5. Can two maps of the different map projection can be overlap onto each other? Provide reasons

Definitely yes. As overlaying data layers from separate sources and coordinate systems can be found in ArcGIS which enable us to intergrate datasets within maps that were in common between map projections

6. 6. Number of GCP we had utilized in georenferencing the aerial photos? Tables of our GCP

We used 6, for the 125.alg

7. 7. What are the criteria of a good GCP

If we are using quadratic polynomial order in geocoding. It requires minimum 6 GCP. But for a good result, we recommend 12 GCP. As for the RMSE (root mean square area) must not be exceeding 1 for any of the points

8. 8. Provide 3 example of good features for GCP

· Road intersection

· Landmark like bridges or railway or buildings

· Natural earth features like lagoons, bays or estuaries

9. What is the min value of RMSE for each point that we manage to achieve

10. Why do you think it is difficult to achieve the RMSE of less than 1 in this aerial exercise

Because this exercise requires absolute patients to plot the exactly points that have similar coordinate with the correct one in the true location

1 11. Why it is important to achieve RMSE of less than 1

In short, RMSE estimate the goodness of the derived transformation. In this process, it measures the fit between the true location and the transformed location of the output control point. The smaller the RMSE, the more precise the point.

Aerial Photographs and Landslide Delineation

Study Area. shp: