There are both terminological and stylistic issues here.

To take the terminological points first, using the Spanish source Phil has kindly provided and an English source I have found:

A. Triangulación is triangulation:

"Metodo de triangulación
Consiste en determinar las coordenadas de un serie de puntos distribuidos en triángulos partiendo de dos conocidos, que definen la base, y midiendo todos los ángulos de los triángulos:"
http://ocw.upm.es/expresion-grafica-en-la-ingenieria/dibujo-... (p. 9)

"1. If you use the triangulation method, you will form consecutive triangles, starting from two known points which you can see from each other. The straight line joining these two points is called the base line.
[...]
2. To determine the position of a new point C by triangulation, this new point is joined to the known base line by two new lines, forming a triangle. You can then find the position of the new point:
- either by measuring the distances of the lines running from the base line to the point;
- or by measuring the azimuths of the two new straight lines running from the points A and B to point C."
http://www.fao.org/fishery/static/FAO_Training/FAO_Training/...

Azimuths means horizontal angles.

B. Radiación is radiation:

"El método de radiación es uno de los métodos de levantamiento de poligonales cerradas, y es el método más simple en el que se emplea el teodolito y la cinta.
Consiste en situar el aparato topográfico en el punto O de coordenadas conocidas, interior al conjunto ABC... que se han de levantar, y tras orientar el
instrumento se determinan los acimutes y las longitudes OA, OB..."
http://ocw.upm.es/expresion-grafica-en-la-ingenieria/dibujo-... (p. 13)

"radiation, a method in which you measure horizontal distances and azimuths, or horizontal angles (see Section 7.2);"
http://www.fao.org/fishery/static/FAO_Training/FAO_Training/...

C. itinerario is traversing:

"Método de la poligonal o del itinerario
La finalidad de la poligonal es determinar las coordenadas de una serie de puntos, muchas veces a partir de las de otros cuya posición ya ha sido determinada por procedimientos más precisos.
Se define la poligonal como el contorno formado por tramos rectos que enlazan los puntos a levantar, que serán las bases o estaciones. Los tramos o ejes son los lados de la poligonal, la unión de bases consecutivas.
La observación consiste en medir las longitudes de los tramos y los ángulos horizontales entre ejes consecutivos."
http://ocw.upm.es/expresion-grafica-en-la-ingenieria/dibujo-... (p. 17)

"traversing, a method in which you measure horizontal distances and azimuths along a zigzag line (see Section 7.1);"
http://www.fao.org/fishery/static/FAO_Training/FAO_Training/...

See illustrations accompanying these definitions.


As for the stylistic issues, this affects the first part. There is a tendency in English educational materials to simpify and cut out unnecessary words. You can put "polygonal shapes" if you like (more common than "polygonal forms" in this field), but polygonal shapes are polygons, and that's what I think would be used in English. And I prefer gerunds (analysing and drawing), because being verbal nouns they put the emphasis on carrying out the operation: actively doing it.

"Analysing and drawing frequency polygons"
http://swanlea.co.uk/wp-content/uploads/2015/08/10_Maths.pdf