503 
ig 2008 
INTRODUCE A 1:500 MAP WAS MADE 
BY THE IMAGE OF “GOOGLE EARTH” AND ITS SOFTWARE 
Ruan Wei 
Professor, retired from survey department of Shanghai Tong Ji University - (Ruan wei 65231125@tom.com) 
Commission III, WG TTT/4 
KEY WORDS: Cartography, Rectification, Photo Map 
ABSTRACT: 
A 1:500 map was made by the image of “Google Earth” and its software (named five points method) quality of the cartography is 
shown on the photo map, it gets great success. Please review it. The experience merits are using only five control points per map. It 
depends upon the rectificated model which is precise and strict, surface fitting smooth 
1. PREFACE 
Forty years of city survey practice is mainly to map by large 
scale. 
r even a 1:1000 one can be ensured. 
We know that Japan has announced its inventory patent which is 
called “ The system of map making and the method of map 
making” in October of 2000 (P2000-298430A). The purpose of 
the patent is obviously to make the city map. However, it needs 
more than nine control points, and the accuracy can’t meet the 
need of the scaled map mentioned above. It’s not practical. 
Can we still put the skill of “GPS + Auto CAD” which keeps up 
with the time into practice? The author must answer this 
question. 
Our successful practice is the best answer. It is practical and 
easy. 
We use “GPS + Auto CAD” as our main tool, and photo map to 
make the map. 
Only use five control points for rectification. We successfully 
make a 1:500 map by using “Google Earth” image. (The 
complete photo map covering 0.21m 2 is available to be 
reviewed by e-mail). 
It strongly shows that by using aerophotograph with high 
resolution, any survey staff can make city map accurately and 
without any risk. 
That is called “five points method” software which is mature, 
reliable, the core of the software design is image rectification 
model 
2. RECTIFICATED MATHEMATICAL MODEL 
The main requirement of the rectificated model is accurate and 
easy to operate. Also, the image in two dimensions can be 
transferred directly. Only N=5 rectificated control points is 
needed for each map. The coordinates of the control points are 
not located in a rectangular array. 
Most people in our country often feel terrified at the 
aerophotogrammetry which is always regarded as a high-tech 
job with accurate and expensive equipment. They think it 
should be very difficult to master its skills. They also doubt how 
the accuracy of making a 1:500 city map o 
We know a linear spline which is based upon the small 
deflection equation of an infinite beam. Obviously, the surface 
spline is a plate of infinite extent that deforms in bending only. 
The differential equation relating bending deflection and load of 
a plate is 
DV 4 W=P (1) 
Where 
D = flexural rigidity of the plate 
W(x,y)= lateral deflect 
P= lateral load 
Under the following suppose; 
1. Deflections are specified at N independent points (x^yO 
i=l,N. this requires points loads Pj at these N point. The 
values of these loads must be determined to give the 
specified deflections. 
2. Deflection is a symmetric deflection due to a point load at 
the point. 
3. The suface spline should become flat a long distance from 
the applied loads 
Then through complex mathematical analysis, the resulting 
equation is rearranged into a form useful for computation. 
N 
W (x,y) = A + Bx + Cy + E Fj Tj 2 In 2 
i = 1 
(2) 
Where 
r| 2 =(x —x,) 2 + (y — y;) 2 
Use Eq.(2), we also add three static equilibrium equations to 
determine the N+3 unknows. 
Use a surface spline to solve it which can achieve good result.