Return to Table of Contents This is the unofficial, WWW version of the VORTEX-95 Operations Plan. It may differ from the published operations plan which is available by 15 March from the National Severe Storms Laboratory.
The pre-photogrammetry surveys must be performed soon after the footage is obtained, before landmarks that appear in the movies can be disturbed, and while camera site markers are still fresh and undisturbed. The first step is to locate the camera site. It should have been clearly marked with spray paint; video images shot during the intercept may prove useful in locating the site. Once located, the survey transit must be set up at the exact location of the camera, and as close in elevation to the camera lens as possible. Level the transit carefully or systematic errors will be introduced into your measurements. It is not necessary that the transit be oriented in any particular direction, but be sure to lock the axis.
While two participants are preparing to use the transit, a third should use the measuring wheel to establish the location of the camera site. Redundant measurements would be desirable. For example: 453 m north of the intersection of the two section line roads, 121 m south of the fence line, and 6 m from the centerline of the dirt road. Reference measurements to features that can be identified on the topographic map, and mark the map with the reference points as necessary.
There are two types of landmarks that must be carefully surveyed at each site. The first are common landmarks that may be visible from both sites, but are not necessarily in both films. Establishing the azimuths and elevations of these landmarks ties the two sets of images together, and allows the establishment of a common coordinate system. The second set of landmarks consists of every possible feature that may appear in the image from a single camera site. This will require knowledge of the scene that was filmed, and can be established from video shot by the team.
When surveying, one participant should record the azimuths and elevations of all the landmarks, and then a second participant should independently measure the azimuths and elevations of the same landmarks (use the Pre-photogrammetry Survey Form found in " Documentation Requirements and Forms" ). Do not share or discuss measurements; these should be independent. Later, the analyst can easily recognize gross survey errors and discard points.
Suitable landmarks consist of the edge of a building (note which edge), the peak of a roof, the center of a tree trunk, fenceposts, radio towers, power poles or power structures, etc. Anything that likely has not moved since the film was shot is suitable. It is vital that you are very detailed in your description of the landmark, so the analyst can later pick the correct landmark out of the image. For example , " power pole" may not be adequate. It may be necessary to record the following: " third power pole from end of row, light colored, used center of insulator at top of pole." You cannot include too much detail.
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