of Surveying and Spatial Information Systems
University of New South Wales
Based Recovery Sketches for the
UNSW Campus Network 2001
by Joseph Cosentino
and edited by J. M. Rüeger
The importance of a good recovery sketch is mostly appreciated, when there is no sketch. The functions of a perfect recovery sketch, in UNSW's view, are to assist to find the mark quickly, to be able to check that the mark is undisturbed and to provide enough information for a replacement of the mark (at least horizontally) in the old position, to millimetre precision, if necessary. This approach was followed when preparing a new web based documentation of the recovery sketches of the UNSW's Campus Network 2001 survey marks.
Properties of the
Perfect Recovery Sketch (General)
The properties of a perfect recovery sketch could not be found in any textbook or other documentation. Here, an attempt is made to define the 'perfect recovery sketch', what it is, what it is used for, and who uses it. A good recovery sketch (see Figure 1) should be up to date, concise and provide all the relevant information. The properties of the perfect recovery sketch depend on the type of area the mark is located in: the sketches of marks in built-up areas and isolated areas will differ. The type of survey, for which the mark is to be used (e.g. high order, control surveys or basic engineering/cadastral surveys), also dictates the design of sketches. The general properties can be adapted for most of these situations. For trigonometric stations, for example, the horizontal position is most important, whereas for levelling marks, the height is most important.
If the mark is on a concrete kerb or in a gutter, at least three basic distance connections are to be measured to well-defined and stable reference marks (drill holes, pegs, nails), services (power poles, man holes, stop valves, gutter inlet pits, any type of pit), or artificial/ natural objects (walls, fences, building, columns, posts, streets, driveways). If the mark is placed elsewhere, at least four basic distance connections are to be measured to well-defined and stable reference marks, services or objects. For both situations, measure the distances along the ground, unless specified otherwise. All basic distance measurements must be to the nearest millimetre and in a star pattern. This way, the marks can be replaced and reset, if required.
Giving approximate distances (to the nearest metre) to nearby street intersections, or (to the nearest 0.1 m) to domineering trees, makes finding the marks quicker. A small-scale locality sketch should be part of the sketch of individual marks, if outside built-up areas. Information on the surrounding area should be included, such as the name of suburb, place, buildings and roads. North is up the page, where possible, and a north point is to be drawn. The material or type of mark should be acknowledge (e.g. drill hole, peg, bolt and any others). The coordinates and elevations are usually kept separate from sketches because they are maintained and changed at different times. The history of the mark should be described (e.g. when it was placed and by whom). A photograph, showing the marks and important landmarks around it, further simplifies the identification.
Figure 1: Sample recovery sketch prepared to new specifications (B406)
Web Based Recovery
Sketches for the Campus Network 2001
The reconnaissance of the marks involved finding the marks and checking, that the marks were in their original position. For the latter, the recovery sketches needed to be cross-examined in the field. Also, a photo had to be taken of every mark. Lists of the marks, that were found, and of the marks, that were not found, were kept.
The computer processing for the recovery sketches required the scanning, the formatting and the compressing of the sketches. The computer processing for the photographs required the down-loading of the digital photographs, the scanning of historical photographs and the editing, formatting and compressing of all photos required for mounting on the web page
Design of the Web
There are two ways on how the individual recovery sketches can be accessed from the start page of the site. The user can select a TEXT version or a MAP version, depending on requirements. If TEXT is chosen, then a choice of three sorted data sets is available, so that the recovery sketch of a point, or those of a number of points, can be found quickly. If MAP is chosen, a small-scale map of UNSW is shown; clicking in the area of interest produces a larger scale map of the selected part of the Campus. Both images have selectable sections so that a recovery sketch may be found quickly. The structure of the recovery sketch web site is best seen in the flow chart in Figure 2. Dreamweaver Version 3 (by Macromedia) was used for the creation of the hundreds of pages of the Web Based Campus Network Recovery Sketches. These sketches can be accessed through the home page of the School of Surveying and Spatial Information Systems of UNSW.
Figure 2: Flow chart of the structure of Web Based Campus Network Recovery Sketches site.
Conclusion and Recommendations
One part of this project, that could have been sped up greatly, was the field work. The introduction of a sequential point list, which determines the marks closest to each other, would have been a great help. Dreamweaver could also have been used more efficiently (for example by using 'templates') to create the 221 similar pages for the recovery sketches. Better coordination and communication with the other students, who were measuring the Campus Network in 2001 and also placed many new marks, would have been of great benefit, too.
The obsolete plan of the Campus Network marks, that was created in 1997 and which was received at the beginning of the project, was of little help, because of the major construction work that occurred over the last five years. If construction work on the UNSW Campus continues at the current pace, I recommend that the web based recovery sketch catalogue be revised every two to three years. The next person to update the UNSW Campus Network Recovery Sketches should learn from the experiences reported in the thesis. In hindsight, the work could have been carried out much more efficiently.
For more information contact:
J. M. Rüeger (supervisor)
School of Surveying and Spatial Information Systems
University of New South Wales
UNSW SYDNEY NSW 2052