Is Bentley surveying applications including this kind of string handling?
String Handling in Survey
This describes how I wan´t the application to handle construction of strings from the incoming
survey points. A string often represents a linear feature such as a center line
of a road, the edge of pavement or a river bank. These are often displayed as
linear elements in the survey drawing. When surveying such features, one needs
to control which points belong to the same linear feature and where another
linear feature starts.
The application should be capable of using several different methods to break
strings or to construct strings. Some of these methods require that the
incoming survey file contains string numbers. Some of the builtin file formats
include specific logic for starting and terminating strings.
Normal case:
A string consists of a number of consecutive points that have the same feature code. The
actual drawing rules assigned to that feature determine whether those points will
generate linear elements or single point elements in the survey drawing.
A string is terminated whenever a point has a different feature code than the
previous point. If feature code remains the same, the point belongs to the same
string as the previous point. This means that a problem arises when the
surveyor moves from one linear feature to another similar linear feature using
the same feature code. For example, measuring points along the left river bank and
then moving over to measure points along the right river bank. If nothing
special is done, the application will incorrectly connect the last point of the
left river bank with the first point of right river bank. The simplest way of
solving this problem is to survey something else in between - a leveling point for
instance.
Handling break code
A break code is a special survey code that will not generate anything visible in the
survey drawing. It is reserved just for terminating or breaking strings. The
coordinates of a break point are ignored. The surveyor can record one point as
a break point before moving from one linear feature to another similar one. You
can define what survey code will be interpreted as a break code with each file
format.
Handling Indexes
User defined file formats include like an setting called String have contiuous point index.
If this toggle is on, point indexes can act as terminators. Consecutive points
will belong to the same string only when the point index remains the same or
increases by one.
Handling String numbers
Some file formats can contain string numbers. If so, those will be used in determining
where one string ends and another one starts. Consecutive points will belong to
the same string only if their string numbers are equal.
Furthermore, it is possible to use string numbers to construct strings from
non-sequential points. For user defined file formats, this will be determined
by the Join disjoint strings by number setting. If sorting is used, the surveyor can freely
choose the order in which he measures points as long as he assigns a string
number for each point in a linear feature.
This is most often used to enable cross sectional order when surveying
longitudinal objects. For example, a road could be surveyed as three linear
features: left edge (EL), center line (CL) and right edge (EL).
The surveyor can choose the order of points freely. The picture above shows the
original Point order as point index labels.
Handling Sectional master codes
Keying in string numbers for each point can be a tedious task for the surveyor. As an
alternative, The application should also supports sectional master codes. These
are survey codes which are actually linked to a user defined list of feature
codes. A feature code can be defined as a sectional master code using the
Option button in the Feature code dialog.
For the case in the picture above, you could define a feature code (RS) as a sectional
master code and link it to a list of feature codes EL, CL and EL. Furthermore,
you could set the reverse order toggle on so that the sequence will automatically be
repeated in reverse order.
The surveyor can then use a single survey code (RS) for all of the points. First
point in a sequence will become an EL1 point, second a CL2 point, third an EL3
point, fourth an EL3 point, fifth a CL2 point, sixth an EL1 point, seventh an
EL1 point and so on.
The advantage of this method is saving time out in the field. The surveyor does
not have to change the survey code and does not have to type in string numbers.
The obvious disadvantage is that the surveyor must carefully follow a certain
order in measuring points.
Best Regards
Tom Lillhannus
