Table of contents:
Video: Applied Geodesy. How To Understand The Estimate
2023 Author: Douglas Hoggarth | [email protected]. Last modified: 2023-11-26 20:16
Where to begin
- 1. Collecting data about the topographic base
- 2. Manufacturing and laying of geodetic marks
- 3. Creation of filming justification
- 4. Creation / updating of engineering and topographic plans
- 5. Planned-high-altitude points fixing
- 6. Executive survey of engineering communications
- 7. Office work
- 8. Other costs
Articles from our series "Applied Geodesy" gave you an overview of the industry and the work performed. There are some things you can do yourself, but most of the processes should be entrusted to specialists. It is the question of reading and checking estimates for geodetic work that will be covered in this note.
Where to begin
The basis of any work is a technical task. It is in it that you prescribe with the contractor not only the timing of the work and the responsibility of the parties, but also indicate additional requirements, which will then be included in the estimate. And here we need to decide - why do we need such work?
You need a project to build a residential building and connect it to city communications. In this case, the work is carried out in the state system of coordinates and heights, passing a number of necessary approvals. Here you cannot do without a licensed specialist or company, and the contract and estimate will become a supporting document in resolving controversial issues.
You want to do a site layout or axle layout for a light construction. This work can be done independently by studying the articles of our cycle, or by inviting a specialist directly, bypassing the bureaucratic red tape. The survey can be carried out in a conventional coordinate system, and the result obtained will meet all the requirements of the legislation no worse than the official work.
When ordering work, you must study the order of prices in your region. Initial data for budgeting:
- purpose of the work
- shooting area
- period of execution
Let's take an estimate template as an example and try to figure out what we can save on and which processes we don't need at all.
to perform topographic and geodetic works
SBC-2004. Approved and put into effect by the Decree of the State Construction Committee of Russia No. 213 of December 23, 2003
|Justification we stand.||Name of works||One. rev.|
|p. 107, v. 81, p. 4||Collecting data about the topographic base||1 object|
|Manufacturing and laying of geodetic marks|
|vol. 46, item 10||Item SS (filming net - metal pin or tube on concrete)||1 character|
|vol. 46, item 11||Work items: metal tubes, pins, dowels, nails, etc.||1 character|
|Creation of filming justification|
|Determining GPS points||1 point|
|p.74, v.47, p.1||Positioning of the anchored theodolite moves||0.6 miles|
|p.74, v.47, p.3||Technical leveling (traverse referencing)||0.6 miles|
|p. 24, vol. 9||Creation of engineering-topographic plans M 1: 500, cross-section of the relief with contour lines every 0.5 m|
|Updating of engineering and topographic plans M 1: 500, cross-section of the relief with contours every 0.5 m|
|p. 24, vol. 9||undeveloped area||1 ha|
|built-up area||1 ha|
|industrial sites||1 ha|
|Planned-high-altitude points fixing|
|p.75, v.48, p.1||up to 50 m from the shooting point||1 point|
|p.75, v.48, p.2||over 100 m from the shooting point||1 point|
|Executive survey of engineering communications|
|p.63, v.37||Survey of exits of underground structures||1 point|
|p.63, v.37||Filming of aboveground structures||1 point|
|p.63, v.37||Leveling the exits of underground structures||1 point|
|p.63, v.37||Leveling overground structures||1 point|
|p.64, v.39||Compilation of a description of underground and aboveground structures||1 well|
|p.64, v.39||Compilation of a description of underground and aboveground structures opened by pits||1 point|
|p.66, v.40||Survey of underground utilities using a cable detector||1 point|
1. Collecting data about the topographic base
Any work begins with an acquaintance with the object. The specialist needs to understand where the survey area is located, which nearest points of the state geodetic network should be used, what is the estimated distance from the enterprise base to the object, and other data. If you have several plots, accordingly, the estimate should contain the required number of objects. In the case when you have two survey sites, there is a distance of 250 meters between them, and the estimate is "1 object", this means that 250 meters between the sites you do not need are included in the cost of the work.
The cost of the work is influenced by the coefficient, which takes into account the density of the soils into which the point will be fixed:
- light uncoated soil
- asphalt, medium hard soil
- concrete pavement
2. Manufacturing and laying of geodetic marks
Laying the theodolite course, competent specialists secure the survey points (SS) and work points. It is likely that after the survey, you will need to perform a number of works on the site, namely, setting out boundaries or executive survey of communications. To do this, the performer will again have to make a theodolite course, which will undoubtedly be reflected in the final cost of the work.
So if you have this item in the initial estimate, and after a couple of months it will be included in the estimate again, hand the contractor a shovel and offer to find the items for which you have already paid money. The shelf life of wooden stakes is 3 months, and metal tubes or dowels - until the metal is destroyed. As you understand, if the destruction of the items happened through your fault, their bookmark will be repeated, but at your expense.
3. Creation of filming justification
To survey the territory, the performer needs to lay a theodolite path or use the capabilities of satellite geodesy. And at this stage, you need to be very careful, especially in the case of GPS. Unobtrusively ask the performer - how old is his instrument this year? If the company owns modern GPS, which allows receiving the coordinates of points in real time, everything is fine. If the instrument is 10 years old, and the survey area is built up and surrounded by tall trees, measurement errors are possible, which may come up at the most inopportune moment after the work is completed.
The number of starting points according to regulatory documents from which the survey justification will be created should be at least 3, two GPS points are allowed, one is the initial, the second is control, but if there are more or less of them in the estimate, you should ask the designer a question.
If your site is surrounded by tall buildings, it makes sense to use the methods of "classical" geodesy - ask the contractor to work with an electronic total station from polygonometry points.
Let's consider the most typical cases with examples:
a) "Hanging" theodolite course.
The most unreliable method of shooting, in which it is difficult to control the obtained values. Here "PP 1 and 2" are the initial points of polygonometry, "hanging 1" is the point of the hanging path, the lines show the directions of measurements. It is allowed to lay no more than two such points. If the performer has recorded two starting points in the survey estimate, ask if he is going to work from a move that literally "hangs in the air"?
b) Closed theodolite course.
As can be seen from the schematic drawing, in this case the performer controls the obtained values, which allows him to be confident in the quality of the work performed. Another option for a controlled move involves the use of four points with known coordinates:
As you can imagine, the performer should ideally use at least two starting points, and preferably three or four. If the estimate says otherwise, it is possible that the performer is cheating or incompetent.
4. Creation / updating of engineering and topographic plans
The two processes are related, but you only have to pay for one of them.
Creation is shooting "from scratch" of the territory. Suitable for new objects, i.e. those that have been significantly rebuilt, or which were filmed a dozen years ago. In general, topography is relevant for a year. During this time, changes could have occurred, for which it is enough to update the engineering and topographic plans. The performer is provided with the original of the topographic survey of a year ago, on which he makes the difference in measurements using an instrumental method. If you have provided the material, or the contractor has it, and the estimate contains "the creation of engineering and topographic plans", it makes sense to offer the contractor to simply update the existing survey. Accordingly, the price for this type of work will be much lower.
The cost of work is affected by the congestion of the territory. The easiest option is an undeveloped plot outside the village. From two points determined by GPS observations, all the work can be done. The built-up area implies an increase in the number of survey points, and the industrial site is generally an object of increased danger. Constantly moving machines and mechanisms do not contribute to fruitful work, it is possible to destroy survey points and create obstacles for measurements.
5. Planned-high-altitude points fixing
The principle applies here: “the more we hand over, the better”, but up to a certain point. The norms define the number of points per survey area plus places that fall out of the picture. It is impossible to predict this indicator, but you should know that 8 survey points per square 50x50 meters are enough for undeveloped territory, plus places of relief changes. Usually this serves as a place for "adjusting" the estimated cost of work to the needs of the customer, but in any case, you need to know the norms.
6. Executive survey of engineering communications
This term refers to the survey of already laid networks. If this indicator was already included in the initial cost of the work, you do not need to order a separate topographic survey to commission the object.
Here it is necessary to note a number of points that affect the cost of work. Ideally, all communications should have a binding passport, copies of which are deposited with the architecture authority, the customer, and remain with the contractor. In practice, it is not possible to find out where the communication takes place without drilling control holes in the ground, called “pits”.
One of the solutions to the problem is to use a locator. This device structurally consists of two parts: a generator, which is connected to the required core of a cable or pipe, and a receiver, which catches the generated signal under the earth.
At this stage of work, it is not worth saving - the communication certificate does not always reflect the real situation. Do not forget that damage to the main pipe entails various kinds of responsibility, so you should not trust the filming materials of previous years. Order instrumental control of underground networks, so that later you can be sure that you will not leave an entire microdistrict without water or gas.
7. Office work
This tricky term means processing the received values. Plans of the area, underground and aboveground structures are drawn up, profiles are drawn and a catalog of coordinates is formed. It makes sense to pay attention to the end result - what do you get your hands on? The result of the work should be a topographic plan on a scale of 1: 500 with the application of engineering networks. If you need an electronic version of the document, ask in which program it was created. The fact is that standard image editors of the operating system do not always understand the format of the data produced by specialized software used in geodesy.
8. Other costs
Everything that was not included in the estimate will be displayed in this section. The main indicator is transportation costs, travel expenses for performers and the coefficient of work complexity. The further the enterprise base is from the object of work, the more voluminous the overhead costs will be.
In this place, the main nuance is buried - who to entrust the shooting, local specialists or invited "stars". There can be one criterion - recommendations, personal communication and knowledge gained after reading our article. It is not always cheaper where - better, especially when it comes to geodesy issues. You rarely order this kind of work, so you should pay attention to the estimate that you are offered to sign.
If an organization is ready to rent 20 hectares per day with a theodolite, using two polygonometry points, it is clearly not worth ordering work from such people. Processes of work that you do not need speak of price hikes, or even fraud. So remember: forewarned is forearmed.
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