EVOLUCIÓN DEL

8. Location Reference Point Surveys

Introduction

Overview

The Location Reference Point (LRP) Survey is used to establish the chainage of the various LRPs. As discussed in Section 0, these LRPs are any permanent fixture adjacent to the road, for example km posts.

By having regular LRPs the data collected in the roughness survey can be accurately related to the same sections of road, even when the survey is conducted in different years.

The LRP Survey allows the operator to record both the chainage of the LRPs and their identifiers. At the same time, they can do keyboard rating of events and store GPS data if the vehicle is fitted with a GPS receiver.

Establishing LRPs

LRPs can be surveyed using either a dedicated LRP survey or during another survey, such as a roughness survey.

It is strongly recommended that LRPs be defined in a separate survey to the roughness survey. There are two principal reasons for this:

 the LRPs are the basic description of your network and they should be located as accurately as possible. Since the roughness vehicle will generally be travelling at a speed above 30 km/h such accuracy is difficult to achieve;

 if you have existing markers, such as kilometre stones, it is often necessary to stop the vehicle to read the marker, to remove grass or debris which may be obscuring it, or even to find the marker.

This is impossible during a roughness survey.

LRP Records

During LRP surveys it is advisable to also take digital photos of the LRPs and record LRP diagrams.

These can be retrieved in computer applications such as the HDM-4 Information Management System (www.hdm-ims.com) and will ensure that the LRPs can be found in future surveys. The figures below are examples of this from an LRP survey in Samoa.

LRP Diagram >

<LRP on Bridge

LRP on Culvert ^

LRP Setup Options

LRP Setup Options

 LRP Reset Method: This option determines how LRP current chainage are to be recorded. Manual resets mean that the operator must press the ESC key to physically record the current chainage of the LRP; Automatic resets automatically reset the readings when the vehicle chainage corresponds to that of the LRP chainage in the LRP file (i.e. it is assumed that the vehicle will record the same chainage at the LRP as that recorded in the LRP file). It is highly recommended that this parameter be set to MANUAL since there will always be slight differences in the LRP chainage between surveys (see Section 0).

 Chainage Reset on LRP Reset: If set to Yes (the default) the survey chainage is reset to zero as a LRP location is marked all subsequent chainages are then relevant to the Last LRP.

 Sampling Intervals reset on LRP Reset: If set to Yes (the default) is yes as normally the sampling intervals should be reset at LRP’s

 Warning Beep in Advance of LRP’s: Setting this to “Y” warns the operator through audible beeps that an LRP is approaching. Beeps are given every 25 m before an LRP, starting at 100 m. It is recommended that this be enabled.

Default LRP Settings in Survey. This option defines whether or not to default to using LRPs. The options available are:

Yes Use an existing LRP file

No Don’t use LRP’s

Define Add or define new LRPs

If you are defining LRPs (D), consider using the Predefined LRP option (see Section 0). This allows you to define a short keycode associated with a longer description, making it easier to ensure consistency during the survey.

 Take Digital Photos when defining LRP’s: This option is used to assign digital photo numbers when defining specific LRPs. In the survey the vehicle will stop adjacent to the LRP and take a photo with a digital camera. Upon noting an LRP the operator will record the LRP data as in the standard survey. If this option is selected they will be asked to enter the digital photo number.

 Name of LRP Definition Table: The default table name in the …/ROMDAS/Setup/LRP.MDB file is LRP_DEF. This can be changed by entering another table name here.

8 Location Reference Point Surveys

 Use Predefined LRP entries: As described in Section 0, it is possible to predefine the LRP descriptions. This means that during the survey the operators only need to enter a short code to insert the full LRP description entry. Setting this option to Y means that these definitions can be accessed when the ALT key is pressed during the survey.

Executing the Survey

Starting the Survey

Select New Survey menu option and enter the survey data into the Survey Setup screen as per Section 0 and proceed to the Survey screen.

The screen below will be shown. Since LRP surveys must always start at an LRP, the start name must be entered to continue.

Press the Space Bar to start surveying.

During the Survey

When an LRP is reached press the INS key to enter the new LRP. The window below will open and the LRP description is entered.

The display will list the distance from the last LRP as well as the total distance travelled (see below).

Using Predefined LRP’s

Instead of using the INS key to mark the LRP and have to type in the LRP description you can use the Predefined LRP’s option to automatically define the LRP. You must have the required LRP descriptions entered into the Predefined LRP definition table (see Section 0) and the LRP Predifintion feature enabled in the Tools | Options | Location Reference Points menu.

8 Location Reference Point Surveys

Pushing the ALT key (instead of the INS key) will bring up the Pick Predefined LRP list. Select the predefined LRP key or you can return to the Define LRP dialog to enter your own description if required. In fact you can change back and forth between the Pick Predefined LRP and Define LRP dialogs by using the ALT and ESC keys.

Ending the Survey:

At the completion of the survey press the F10 key. See Section 0 for further options when ending the survey.

Example of Data:

A full description of the data is given in Chapter 20.

Continuing Previous Surveys:

The Continue previous surveys works in the same manner as described in Section 0 for keyboard rating surveys.

Digital Photographs

Overview

Digital photographs can be used to record the LRP features when defining LRP’s. As many photos as required can be taken at each LRP.

Setting Up the Camera

The setting up of digital cameras is described in Section 0.

Setup

The Take Digital Photographs at LRP’s option must be enabled.

During the Survey

Whenever a LRP is defined the Take Photo dialog above appears allowing one or more digital

photographs of the LRP to be logged. For each photograph the incremental photo number is displayed.

This can changed if required. A comment can be entered if required. If more than one photograph of the LRP is required then the Another Photo button should be used else select Finished to exit the dialog.

Example of Output

An example of the photo data from the survey is shown below. A full description of the data is given in Chapter 20.

The photograph for each LRP is recorded in the Set_Number field in the LRP_ table. The photograph numbers and file names for each Set are recorded in the Set_Number and Photo_Number Digital_Camera_Picture_ table