Product Profile

July 1, 2005
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Topcon's GPT-7000i Imaging Total Station is a full-featured total station that houses the innovation of a built-in camera mounted coaxially with the instrument telescope. This instrument offers new possibilities for surveyors that are not feasible with any other instrument, including direct visualization of stakeout points, visual blunder detection and a "telescope view" record of the survey work that has been done. The basic specifications for this instrument read like most top-of-the line total stations: angle accuracy of ±1, 2, 3 or 5 seconds, EDM accuracy of ±(2 mm + 2 ppm) for measurements over 25 m in prism mode and ±5 mm in non-prism mode. As part of Topcon's advanced 7000 series, the GPT-7000i shares with other instruments in the series: onboard applications to carry out a variety of advanced survey procedures provided by TopSURV software and a color LCD touch-screen display in addition to a keyboard for machine interaction. Then you notice the first big difference: 256 Mb of onboard flash memory. Why so much? Because the total station takes pictures, too.

The wide-angle images are displayed on the 1⁄4 VGA (640 x 480 pixel) screen, allowing the surveyor to document the scene as viewed through the telescope. The instrument will also automatically photograph the surroundings where every shot is taken. The intelligent software doesn't fill up the memory with a lot of redundant photographs; it determines if each survey shot taken has already been covered in an existing frame, and only takes a picture if it hasn't.

Additionally, the camera provides a live video feed when aiming the telescope, fulfilling the dream of some surveyors who wish they never had to peer through a tiny eyepiece. The position of the crosshairs appears on the screen, and for many applications, can be aimed at the appropriate target with ease and accuracy. Users can zoom to a higher magnification, which is useful for pointing under difficult conditions. It also makes the laser pointer dot more easily visible under poor sighting conditions or when the target color blends with the laser dot. When doing control surveys or other high precision work, the surveyor will still have to do the math to determine the real-world size of each pixel to know whether using the camera to aim is sufficiently accurate.

The photographic eye of the total station has other operational benefits as well. It is quite common for surveyors to point their telescopes at targets, pause briefly to do something else, and then continue the work assuming that the telescope orientation has not changed. The onscreen view of the GPT-7000i's telescope aim can be easily used by the surveyor to verify that aiming errors due to settlement, vibration and minor bumps haven't occurred. Similarly, the surveyor can use the camera view to determine that the operation of aiming the telescope at the target has not been finished.

Being able to visualize the work being done has always been one of the surveyor's significant challenges. Being able to move quickly and accurately depends greatly on an individual's ability to judge whether the points being mapped or laid out are properly spatially related. With the GPT-7000i, each measurement taken is represented on the screen image. Even if the instrument is rotated away from the point, so that a different part of the horizon is on the screen, the surveyor only needs to rotate the instrument back to see the point again in proper context. This review of the work can also be done in image viewing mode; the surveyor can see all images and registered observations, regardless of where the camera is pointing-it doesn't even have to be set up at the station from which the images were taken. Whether they are mapping or setting out, users can apply functions to represent points with different symbols or to connect them with lines to develop a more visually sensible overview of the work. When the work to be done is stakeout, the points to be staked can be visualized on the screen too, after the instrument and the image have been properly oriented and coordinated.

Although the use of the basic surveying technology of the total station is not changed with the GPT-7000i series, the camera adds several enhancements that enable the surveyor to work with greater efficiency. Another feature of the 7000i series that expands its basic functionality and changes the end product is the ability to take photogrammetric images. With an advanced GPT-7000i model, users can take pictures of an area to be measured, move the instrument along a "baseline" to a new setup and take another set of pictures, then view the pictures stereoscopically. Surveyors familiar with the principles of photogrammetry will recognize that the X, Y, Z coordinates of the total station's measuring points then become the coordinates of the camera stations. Because the total station can also determine X, Y, Z coordinates of photo-identifiable points in the photographs (that is, photogrammetric control), it is now possible, using the appropriate software to map (and essentially develop coordinates for) all the features visible in the scene covered by the overlapping photographs.

The GPT-7000i series models have suggested retail prices ranging from $15,290 to $20,490, a premium of about $4,000 over the similar GPT-7000 (non-camera) models. This includes the instrument kit (with case, batteries, charger, etc.) and on-board TopSURV software providing all the capabilities of photo capture, digital stakeout and topo point projection on to live image, as well as digital linework and image capture for 3D modeling.* For that premium, many surveyors will find it worthwhile to investigate the features and benefits of the GPT-7000i series to find out whether it will help them work better, faster and cheaper.

Topcon's GPT-7000i represents the first advanced embodiment of camera technology integrated into a total station. Perhaps it is the precursor to more advanced systems that integrate more features of machine vision and other automated analysis functions. But even in its current form, surveyors are likely to appreciate and use the benefits provided by the camera to survey more accurately, more quickly, with less unnecessary repetition of work. There are also opportunities to use the imaging features to sell clients on the new information that can be provided them, illustrating the work with the total station's pictures and the annotation of the point and linework that was done. It may become easier to show clients what has been done or what is being proposed. It may also help them to literally understand the surveyor's point of view. Considering the many times surveyors feel underappreciated by clients, there is high potential for education of the people to whom survey data is delivered.

* Users who wish to take advantage of the photogrammetric features of the GPT-7000i will incur additional costs for the 3D imaging software. Topcon anticipates these software products to be available in a version that provides a full photogrammetric solution as well as a light version with essential but reduced functionality. This (desktop only) software is anticipated to be released this month.

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