Drawing up plans and surveying the area is carried out by topographers using special tools. You can shoot with a tablet. This type of photography is called eye-based photography. In addition to a tablet (sheet of plywood or cardboard) and, for such shooting you need a sight ruler, compass-measuring device and a pencil. Before you start shooting, it is very important to choose the right one. When choosing a scale, the size of the area and the size of the sheet of paper on the tablet are taken into account. After selecting the scale, the tablet is made. To do this, the tablet must be rotated so that the letter C (north) on the compass scale coincides with the northern (dark) end of its magnetic needle. In this case, the compass needle should be parallel to the edge of the tablet. After orienting the tablet, you can determine directions to surrounding objects and distances to them. Directions are determined using a ruler, and distances are determined in pairs of steps, then the distances are converted to meters depending on the length of one pair of steps.
Eye survey can be carried out from one point or while moving around the area. When surveying is done from one point, this is polar surveying, and when surveying the area is carried out while moving along any route, this is route surveying.
Polar photography.
To get a plan open area Polar photography is used in areas. The tablet is installed above the observation point (pole) and oriented. The observation point is marked in the center of the paper attached to the tablet. Then select a scale and, using a sight ruler, draw direction lines to surrounding objects on paper and mark the distances to them in accordance with the selected scale. Geographical objects indicated on the plan using .
Route photography.
Route photography can be done by organizing a hiking trip. To photograph the area along the route of movement, it is necessary to divide the entire path into sections, taking into account all the turns. Each clearly visible section of the path is plotted on the tablet, as in polar surveys. At the same time, the segments of the path connecting the points from which the shooting was carried out are also marked. These segments are plotted on the scale chosen for the entire survey. Along the line of movement, using conventional signs, all visible objects terrain.
SECTION II LAND ON PLAN AND MAP
Subject,PLAN, ITS MAIN FEATURES
§13. DRAFTING A SITE PLAN
Remember what azimuth is.
How can you measure distances on the ground?
METHODS OF DRAFTING A PLAN. Used to draw up a plan. Okomirne surveying of the area. This method is quite simple and even a schoolchild can use it. It is used when there is no need to measure directions, distances and heights very accurately; they are determined “by eye”. There are two types of near-surface surveying - polar and route. Okomirne polar survey is drawing up a plan of the area from one selected point, which is usually called the pole. Regional route surveying is drawing up a plan of the area, moving along a specific route.
To draw up a plan of a small area of the area with your own hands, you need simple tools - a tablet, a compass, a ruler, a pin, a pencil, a sheet of paper (preferably in a box). A tablet is a rectangular board (plywood) on which a sheet of paper is attached and secured in top corner compass (Fig. 44).
A place (point) is determined on the ground from which the entire site will be clearly visible. Measurements are taken from this point. Mark your location on a sheet of paper with a pin. Next you need to prepare the tablet.
The compass is mounted so that the imaginary line that connects the 0 and 180‘ divisions on its scale is placed parallel to the edge of the tablet. On the sheet in the upper left corner, draw a “north - south” line and point with an arrow in the direction of north. Its direction must coincide with the direction on the compass. To do this, turn the tablet around its axis until the northern end of the compass arrow points to the number 0, that is, until the arrow coincides with the direction Hn. - Pd. on a piece of paper. Then choose the scale of the plan and write it down on the sheet.
To draw objects using the polar method, place a ruler on the tablet so that one end of it touches the pin, and the other is directed at the object (house, tree, bush, etc.) that should be marked on the plan. Using a ruler, draw a line with a pencil (Fig. 45). Then determine the distance to each object. This distance is laid down along which lines are drawn on the selected scale. The object is indicated by a symbol, and the line is wiped with an eraser. This is how other terrain objects are depicted.
Rice. 44. Tablet for removing okomir
Rice. 45. Drawing objects using the polar method
Rice. 46. Okomirne route survey of the area
Convenient and in a simple way creating a terrain plan and local route survey with determination of object azimuths. On the ground, we focus on noticeable objects (mill, house, bell tower, mountain top, etc.). A certain azimuth will always “lead” us to them (Fig. 46). The distances between points are determined by the time spent walking or steps. The planned path will look like a broken line consisting of several segments.
WHY ARE PLANS NEEDED? A terrain plan is a reliable human assistant. According to the plan, they determine where it is better to build a factory or a residential building, where it is more convenient to locate schools and in what places to lay gardens and public gardens.
Before power lines, roads and pipelines are laid, these objects are outlined on plans. Designers carefully study the area according to the plan and determine where they will not have to overcome many elevations and build bridges, that is, they choose a place where it is better to build and construction will cost less. In agriculture, a plan is necessary to determine areas, fields, meadows and other lands. It is used when, for example, time for plowing and other field work circulates in the system.
A plan is necessary for tourists. After all, before they go on a trip, they first get acquainted with the area of travel. During a hiking trip, the plan is used as a guide to navigate the area.
Terrain plans vary. The simplest of them are called schemes. They depict only individual objects. For example, schemes railways, you could see them at train stations and metro lines. They help you navigate the placement of stations. There are plans for your school. In the event of a fire or other disaster, they will help you find exits from the premises.
REMEMBER
· Okomirne survey is the easiest way to draw up an area plan “by eye”: either according to one selected point (polar), or moving along a specific route (route).
QUESTIONS AND TASKS
1. What methods do you know of drawing up a site plan?
2. How does a polar survey of an area differ from a route survey?
3. How do people use site plans?
4. Make a plan on a scale of 1: 10000 according to the description. Not far from the school, about 300 m to the north, there is an oak tree. Further behind it you can see bushes. 100 m to the southeast of the oak tree there is a spring. 200 m from the source further to the east there is a lake, stretching from north to south for 400 m and a width of 150 m. To the north-west of northern shore a windmill is visible from the lake, the distance to which is 200 meters. If you walk 250 m south from it, you can reach the road that leads to the school. In what direction and how far do you need to walk to get to school?
WORK IN A GROUP
Take a close look at the metro map in Kyiv in Fig. 47. Imagine that you need to get from one metro station to another:
group 1 - from the Vokzalnaya metro station to the Maidan Nezalezhnosti station;
group 2 - from the Taras Shevchenko metro station to the Golden Gate station;
group 3 - from the Lesnaya metro station to the Palace of Sports station.
Which metro line should I take? How many stops do you need to go through? Or do I need to change trains to get to another line? Calculate approximately how much time you will spend on this journey if the average travel time between two stations is 2 minutes.
Rice. 47. Fragment of the diagram metro lines in Kyiv
Before making a decision on the construction of new factories, schools, sports institutions, on the construction of roads, on the location of agricultural land, it is necessary to have an image of the given area.
A small area can be drawn or photographed, but many objects earth's surface It will be difficult to determine from such images.
The most common images of the earth's surface are aerial photographs, images from space, maps and site plans.
Plan - drawing of a reduced image of the area, made in conventional signs on a large scale (usually 1:5000 and larger). Usually plans are made for a small area of the area, several in size. square kilometers, the curvature of the Earth's surface is not taken into account. The first maps in history were plans. Plans are used in a wide variety of industries and Agriculture. When constructing buildings, laying roads and communications, you cannot do without them.
Objects located on the surface (forests, rivers, villages, fields, etc.) will be seen better if the area is photographed from above, for example from an airplane. This image of the area is called an aerial photograph. On it, objects are similar to their true appearance on the ground, their sizes and mutual arrangement. There are many differences between a plan and an aerial photograph. A site plan is a drawing on paper depicting a small area of the earth's surface in a reduced form. The plan differs from other images of the surface in that all objects on it are shown by conventional symbols. In general, it is more convenient and more informative to use a plan.
Aerial photograph and site plan:
Rice. 2. Aerial photograph and site plan
Directions on the plan are indicated by an arrow, the tip of which always points north. Usually the north on the plan is at the top, the south is at the bottom, the east is on the right, and the west is on the left. Using the plan, you can determine the relative position of objects on the sides of the horizon and measure the distance between them using a single scale.
Rice. 4. Area plan and symbols for it
The conventional signs of the plan are, firstly, simple, secondly, unlike each other, and thirdly, they resemble the objects themselves. Under these conditions they are clear to everyone who reads the plan. So, rivers and lakes are shown blue water, and forests - green - the color of vegetation. There is no special sign for fields and vegetable gardens, so such areas are left white on the plan. The grassland symbol resembles stalks of grass. Sands are represented by brown dots. Small streams, roads, narrow streets depicted with conventional symbols in the form of lines. Such symbols are generally accepted. They are used on all terrain plans.
Groups of symbols:
1. Area
Which depicts a small area of the terrain on a large scale. If the terrain plan is drawn up on a smaller scale (from 1:10,000 to 1,000,000), then such a plan is called topographic map . A terrain plan is used in various domestic, tourist and economic areas for orientation to the area.
Knowing how to make a plan of a small area of the area, you can make a plan and large territory. The work of drawing large plans is complex, requires great precision and is carried out by topographers using precision instruments. When creating plans, topographers use various instruments with which they accurately determine the position of geographical objects, the distances between them, and their height. Very often they use to make plans aerial photographs, that is, photographs of the area obtained from an airplane. On the plan we see the terrain from above, as if from an airplane, reduced many times.
Creating a site plan
Let's assume that we need to draw up a plan of the area shown in the figure (Fig. 19).
Having installed a tripod with a tablet near the spruce (from here we will start shooting), draw a linear scale and draw an arrow showing the north-south direction. Now we position the tablet so that the direction of the arrow on the plan coincides with the direction of the compass arrow, i.e. we orient the tablet along the sides of the horizon.
All local items, which we will encounter during the shooting, we will put on the plan using conventional topographical signs.
First of all, on the plan we should depict the tree from which we begin shooting, and stick a pin near the symbol “tree”. This will be ours starting point.
Now, having placed the sighting ruler on the tablet so that its edge touches the pin, we aim with its upper edge at another tree growing near the bend of the road, and draw a sighting line on the plan.
After this, we can mark on the plan with a conventional sign the segment of the path from the tree to the bend of the road. To do this, we measure the length of the road section and plot this distance on the plan to scale. In addition, we use conventional signs to show that there is a bush to the right of the road and a meadow to the left. The second stop will be at the bend in the road. Here we install a tripod, orient the tablet, draw trees with symbols and, sticking a pin, aim at the bridge.
Moving from the trees to the bridge, we stop at the house and put it on the plan. Then we draw the bridge. The width of the river can be measured by crossing the bridge and shown to scale on the plan. You can determine the direction of water flow in the river and indicate it on the plan with an arrow.
In this way, a plan of a small area of the area is drawn up. Ultimately, the plan should look like this (Fig. 20).
Nowadays, more and more photographs of the area taken from an airplane are used when drawing up plans. Such photographs are called aerial photographs, and the process is called aerial photography. Using these images, specialists quickly and accurately draw up plans of the area.
Firstly, the scale of the plan is large, for example: 1 cm - 200 m. Geographical maps have a small scale.
Based on the results of a theodolite or tacheometric survey, a site plan is drawn up. The plan is characterized by accuracy, detail and completeness.
The detail of the plan is the degree of similarity of the contours and terrain objects depicted on the plan. On the plan, it is allowed to straighten the contours with an error of 0.5 mm on the plan scale.
The completeness of the plan is determined by the specific conditions of the area and its purpose. Depending on their purpose, large-scale plans are divided into topographical and specialized. On topographic plans all objects and contours listed in the book “Conventional signs for plans of scales 1: 5,000, 1: 2,000, 1: 1,000, 1:500” are applied, and the relief is depicted with the accuracy specified in the Instructions. When creating specialized plans, you can depict not the entire situation, but only what is necessary for the customer, use a non-standard height of the relief section, etc.
Plan accuracy is the average error in the position of an object or a clear contour relative to the nearest points of the survey justification. According to the Instructions, this error should not exceed 0.5 mm on the plan scale; in mountainous areas this tolerance increases to 0.7 mm.
The required shooting scale is calculated based on a tolerance of 0.5 mm on the plan. If the specified error in the relative position of objects in nature is, for example, 1 m, then the shooting scale should be:
1/M = 0.5 mm /1 m = 1/2,000.
The plan is built in two stages, corresponding to the two stages of surveying:
a geodetic base is applied, i.e. points of the state geodetic network, points of condensation networks and points shooting justification according to their known rectangular coordinates;
the situation is applied, i.e. pickets are placed relative to survey justification points in local polar coordinate systems, and contours and relief are drawn.
First, a coordinate grid of squares with a side of 10 cm is built on a sheet of Whatman paper using a special Drobyshev ruler; The coordinates of the corners of the squares are signed. Then, using the coordinates selected from special tables according to the sheet nomenclature, the corners of the trapezoid frames are constructed. Sometimes plans are made not in six-degree, but in three-degree zones.
The error in the position of the vertices of the coordinate grid squares should be of the order of graphic accuracy - 0.1 mm. With a grid size of 50 * 50 cm, a value of 0.1 mm corresponds to an angle of 0.7". No protractor will provide such accuracy in constructing angles, so they use an indirect method for constructing a right angle. Using a Drobyshev ruler, with an accuracy of 0.1 mm, they lay out the legs 50.00 cm long and the hypotenuse 70.71 cm long ; a right angle in a triangle constructed in this way will have the required accuracy.
All points of the survey justification from which the survey was carried out, and points of support networks that fall on this plan sheet, are plotted on the plans according to their coordinates.
Pickets are drawn in local polar coordinate systems using a protractor and a transverse scale or using a tacheograph (a circular protractor with a ruler on a transparent base). Near each picket its number and mark are signed.
Then, using an outline, they draw out the situation in conventional symbols and draw horizontal lines.
The drawn up plan is taken to a site and its control is carried out either by eye or instrumentally. After checking, the plan is drawn in ink in one or more colors, all signatures are applied, frames and outer space are drawn up, and the form is filled out.