1, measuring coordinate system to screen coordinate conversion
2, the same coordinate system transformation: 1, shift 2, 3, scaling, rotation,
3, map symbol categories: point-like symbols, linear, planar
    Design idea: Instead of graphics systems the same way as the realization, 1, in order to CAD-based, 2, according to its own graphics data structures and application development platform for the free
4, wblock and block the difference between: WBLOCK is to generate an external file, BLOCK is generated within the block
5, how to set line and fill styles:
Fill the features of. Pat format is:
* Pattern Name
Angle, x start, y start, x increment, y increment
6, DTM: in digital form, according to a certain degree of structural organization together, indicated that the spatial distribution of the actual topographic features, namely, the size and shape, undulating terrain of a digital description.
DEM: array with a set of ordered values is expressed on the ground floor elevation of a physical model, is a branch of DTM.
7, affect the accuracy of DTM What?
DTM Accuracy: like little bits and density, interpolation algorithms, the choice of data structure
Evaluation of DTM performance parameters: accuracy, computing speed, data processing capacity, user interface, data acquisition workload
8, what is the TIN, rectangular grid
TIN: the direct use of field survey measuring all the characteristics of the region feature points and construct a grid consisting of adjacent triangular structure.
Rectangular grid: The original discrete points, in accordance with interpolation calculation rule to follow the shape of the node grid coordinates are stored in the DTM in the law.
9, the establishment of TIN methods are what and how to handle some special cases, such as fault-line treatment
The establishment of TIN methods: Thiessen polygon method, the recent distance algorithm, minimum edge length method.
Fault line treatment: the input data and pre-processing and classification process, the fault line is extracted and expanded into a very narrow grid bar closed domain.
10, please briefly ascend the line generation process and the basic idea of
To first establish a TIN, and then contour tracking, the final fitting
11, elevation interpolation: According to the coordinates of a given plane P, the use of the adjacent discrete points of known elevation as a reference point to calculate P-point elevation
Algorithm: linear interpolation, high order polynomial interpolation and least squares interpolation, distance weighted average interpolation
12 grid to determine whether there are contour lines: From the rectangular grid of a grid cell edge of the beginning, from the extension of the direction of contour lines, according to a rectangular grid of elevation values of the decision node
13, contour smoothing: linear iterative method, piecewise cubic polynomial, tension spline interpolation, quadratic-weighted average.
14, Calculation of earthwork volume of three kinds of methods:
(1) contour line method
Application of contour calculation of the volume of the basic approach is, first of all planning based on expenditure area surrounded by contour lines, surrounded by two adjacent contour lines is multiplied by the size of the average contour distance, that is, the volume between the two contour lines (ie, earthwork volume).
(2) The Grid method
The Act is mainly used for construction sites larger in scope, undulating topography and ground slope is not a regular region.
  (3) cross-section method
Topographic map in order to roads, drains and other ribbon digging earth structure, fill, they generally have adopted cross-section method
15, TIN advantages: a, the original data as a network node b, does not change the original data and its accuracy c, to retain the original key terrain features d, the use of TIN contour tracking algorithm is relatively simple.