数字测图原理

数字测图原理

Principles and methods of Digital Mapping

Though this course is called digital mapping.It contains two main part.The first part is teaching us the knowledge of surveying.The second part is introducing the principles of digital

mapping.Because our school did’t set the SURVEYING，this couse concentrate on the first part.So we spend two semester to finish this course.

这个课虽然叫做数字测图。但它主要包括了两个方面。第一部分是关于测绘学的，第二部分是介绍电子绘图的。由于我们没有开设测绘学这一门课程，所以这个课程的主要重点是在教会我们测绘学的相关知识。

The first semester is just as a introduction to the surveying.Surveying consist of three parts.The first is leveling surveying.Leveling surveying is mainly to measure the difference of

elevation.through the leveling instrument,we can know the difference of the height between the two points easily.If we know one point’s elevation(usually we will have some points that we have already know.)we can simply get the ather one.The elevation is important because it can show how the surface of our land is.

第一部分告诉我们关于测绘的知识。测绘主要包括三个部分。第一部分是水准测量。水准测量是用来测量地表的高程差的。通过水准仪，我们能够很容易的测出高差。如果已经知道一个点，我们就可以轻易求出另一个点的搞成。 高程是非常重要的。因为它显示了地表的形态。

The second part is angular surveying .Two important angle were mentioned in this part.The vertical angle and the horizontal angle.Through vertical angle,we can calculate the height of our target.And trough horizontal angle,we can make sure the position of the unknown point by the point we already know.usually we use the transit instrument and total station instrument to do this job.

第二部分是角度测量。第二部分是角度测量。两个重要的角度被提到。一个是竖直角，一个是水平角。通过竖直角我们能够计算目标的搞成。通过水平角度，我们能过已知点确定未知点的坐标。通常我们用全站仪跟经纬仪来做这个。

The last thing we need to measure is the distance between the two point.Traditionally we use the ruler to measure the distance.Nowadays people tend to use the laser,which is equipped by the total station instrument.

关于测绘的最后一部分是测量距离。传统的测量距离的方法是用尺子。现在人们测量距离的方法是用激光，而激光测距这个功能全站仪有搭载。

Then ，comes the part of how to mapping.That’s what we learn in the second semester.To

map,we need to survey at first.That is contral survey.The most popular way is triangulation:using straight line to connect different contral point,and shape the as many triangles that connected to each other.By measureing the distances and the horizontal angel ,we can calculate the coordinate of the other point.

Another method is called traverse survey.The principle are the same as triangulation.

接下来说说制图部分。这是我们第二个学期学的。我们为了制图得先测量。也就是控制测量。控制测量最流行的方法是三角法测量。把已知点用直线连接起来构成许多相互连接的三角形。然后测边跟测角，就可以很容易的得到未知点的坐标。还有一种方法是导线测量，原理跟三角高程测量类似。

When we have got all of the coordinate and the height ,we use all those known point to do the next level survey.To draw the spaciel entities,you should first find the point that would discirbe the features like the angle of the house.Measureing all the points’ positions.

What you will do next is to connecte all the points.Then comes to the map.The main point of the digital mapping is to use the digital way to do the traditional way.Like in China,we use the software Cass to do the mapping .It is a mapping software that based on the CAD.And we use the total station instrument instead of the transit instrument.

当我们得到所有点的坐标跟高程。我们就可以用这些点来做下一等级的测量。为了画出地理实体，应该先找出地物的特征点。比如房子的角。测量出这些点。

之后就是连接所有的点，然后画出地图。数字测图的中心就是在于用数字的方法取代传统的方法。比如我们学的CASS 软件，是基于CAD 的一款绘图软件。然后我们一般用全站仪来代替传统的经纬仪来测距。

That is what we learn in this course.

词汇表

测绘学 survey

参考椭球 reference ellipsoid

参考坐标 reference coordinate

投影 projection

分带投影 projection by zones

投影坐标系 projection coordinate system

经线 longtitude circle

纬线 altitude circle

经度纬度 longtitude altitude

相对** relative

绝对** absolute

方位角 Azimuth angle

真北方位角North**

坐标方位角Coordinate

磁北方位角Magnetic noth**

误差error

系统误差 system error

偶然误差 irregular error

方差 variance

比例 proportion

相对误差 proportional error

水准仪 leveling instrument

高程 height elevation

水准尺 leveling pole

等高线 leveling line

竖直角 vertical angle

水平角 horizontal angle

经纬仪 transit instrument

三角高程测量 triangulated height 导线测量 traverse survey 闭合导线 complete loop 三角网测量 triangulation

地形地貌 topographic expression