Development of Software to create a Rectified Image of an Inclined Plane
Figure 2 Creating a rectified image of an inclined plane
2. Outline of Developed Software
2.1 User Requirements
User requests to the software to create a rectified image of a slope were summarized as follows:
- Software should be
operated easily by an amateur. The software will
be operated by a geological engineer or a civil
engineer at a construction site who is not used
to photogrammetry nor image processing. Software
should be operated easily by an operator without
photogrammetric nor image processing know-how.
- Field works at a
construction site should take a short time.
There is a limited time for geological survey at
a construction site. No field works except image
acquisition are usually allowed at a site. It
should be easy for an amateur photographer to
take necessary images. No ground survey of
control points should be required.
- High spatial accuracy
of a rectified image should not be required.A
rectified image of a slope will be utilized for
visual interpretation. Geological survey at a
construction site allows rather lower spatial
accuracy of a rectified image.
- No special equipment should be required.The cost of equipment should be low. All hardware components should be inexpensive, and they should be for all purposes and available on the market.
2.2 Processing flow
In order to answer the above mentioned user requests we developed a piece of software to create a rectified image of a slope based on the assumption that the target slope is a plane. Figure 3 shows the processing flow using our software. Outline of each step will be explained in the following section.
Figure 3 Processing flow using the developed software
2.3 Image acquisition by digital camera
A pair of scales such as staffs in leveling laid in parallel on a target slope is photographed in both sides of an image as shown in Figure 1. This gives geometric controls such as length and straightness in determination of transformation equation of each image. Furthermore this ensures that there is no gap between adjacent images.
Figure 4 illustrates acquisition of a series of images with a pair of scales. Image 1 and Image 3 have Scale I in the left side and Scale II in the right side. In reverse, Image 2 and Image 4 have Scale I in the right side and Scale II in the left side. These movements of Scales I and II are the same as the movements of staffs in leveling.
