PREPROCESSING PROCEDURES FOR AUTOMATIC PLOTTING IN 
PHOTOGRAMMETRY x x Na 
Elena Agnoletto Baj , Luciano Azzarelli , Massimo Chimenti 
Ovidio Salvetti 
**Ist. Elaborazione dell'Informazione, CNR, Pisa, Italy 
*ist. Geod.oTop. Fotog., Fac.Ing., Univ.of Pisa, Italy 
Working Group II/2 
3 
1. Introduction 
In the last few years a new photogrammetric methodology has been 
studied for particular applications in close range photogramme- 
try; generally it is called raster-photogrammetry. 
The methodology requests that a reticle is projected onto the ob 
ject to be taken and it has mainly two advantages: it needs only 
one photogram instead of the stereoscopic pair and it makes easi 
er the automatic reading of the plate-coordinates and consequen- 
tly the automatic plotting, 
In order to obtain a precise raster photogrammetry we need espe 
cially a precise projector during the taking. Then, if we proce 
ed with automatic reading of plate-coordinates, we need to acqui 
re the image and then to process data with a digital computer. 
In this paper we report about the projector, the scanning device 
and the preprocessing procedures. 
In ref.[1] an example of plate-coordinates reading is shown, 
which was performed on data that have been acquired by using so 
me devices and the preprocessing procedures described in the fol 
lowing. 
2. The Projector 
The projector is really different from a normal one; we will call 
it "metric projector. 
First of all ít will have the same precision of the metric came 
ra it works with (from the mechanic point of view as well as 
from the optic-one) and it will work on a tripod. 
ci 
O 
As it is very important direct easily the projector towards 
the Object to be taken, it will consist CE two rain parts: an 
orientable support and a tiltable projector; these rotations,mea 
surable on horizontal and vertical. circles allow.the projector 
to assume the exterior orientation requested (fig.1). 
pee 
In a metric projector, like in metric camera we have to define 
the interior orienta! z a