Point of Beginning

In Review: SMI Construction Five

December 1, 2001
Discover why SMI deserves serious consideration when considering a change in data collection software.

Surveyors Module International (SMI)
412 Payne Ridge Road
Church Hill, TN 37642
800/234-0123
www.smi.com

Suggested List Price: $1,600

Figure 1. Multiple angle results.
Although the Hewlett-Packard HP48 has its advantages as well as its constraints, it is found in almost every surveying firm and is the only field computer in many. Surveyors Module International (SMI) of Church Hill, Tenn., is one of the few firms that offers surveying software for the HP48.

SMI recently released Version 7 of its surveying series for the HP48GX. This series includes Basic COGO, Standard COGO, Advanced COGO, Data Collection, Construction Five and GPS/Robotic.

This review is based on Construction Five, which contains all of the surveying series listed above except GPS/Robotic.

Functions

Construction Five contains a full set of COGO functions including angle and compass adjustments, rotations, transformations, setting point stakes, staking complex road projects, computing volumes and storing cut sheets—just to name a few. Nearly 100 functions are accessible directly from the keyboard while others appear as submenus of the first list. This review will touch on a few of them.

Data Collection

One of the major functions of a data collector is to obtain topographic information including attribute data. The SMI note field can hold up to 255 characters that can be split into two parts called the note field and the code field. These fields default to 30 and 16 characters, respectively, when converting raw data to coordinates. There is an option to change these values when downloading data, but if it is necessary to edit the raw data and regenerate coordinates, the default values are always used. The requirements of the software used to process this data are the determining factors in how this data should be entered. If more attributes are needed, any programmer can access the ASCII-based raw data file and parse the description field to translate the data into the desired format.

Multiple Angles (Set collection)

Note 5 of the ALTA/ACSM accuracy standard states that “Any angle measured that exceeds the specified amount from the mean must be rejected and the set of angles re-measured.” SMI makes this job easy by displaying the results of all angles as shown in Figure 1. All face 2 shots are stored as the face 1 equivalent and tagged with an R to indicate a face 2 observation. The user then has the option of re-shooting any that need to be rejected. This is as simple as keying the set number to be re-shot and pressing the SETx softkey. However, the replaced records are not retained in the raw data, providing no record that a set was rejected and re-shot.

The number of sets is open ended, i.e. there is no need to predetermine the number of sets to be taken. The user can stop whenever the necessary accuracy has been determined. However, there is only room on the HP48 screen to display the results of three sets, so only the last three are displayed. I would like to see an option to scroll back to observe earlier sets.

Multiple angles can be taken to an unlimited number of locations without the need to shoot the backsight for each location. Once a direct and reverse point sequence has been established, it is no longer necessary to key in the point number being observed. If an instrument with a servo motor is being used, it will turn automatically to the next point and the scope reversed if necessary. SMI does not record the distance to the backsight when using the multiple angle function. I would like to see this option added.

Remote Objects

In addition to the common ability to locate an object using horizontal and vertical offsets, SMI provides the ability to locate objects both horizontally and vertically without placing a prism on or near the object. This is accomplished by observing the object from two different locations, and the coordinates determined through triangulation. In addition to coordinates, accurate elevations can be determined if the instrument is aimed at the same spot from each location and the instrument HI has been properly established. Any number of inaccessible objects can be in the queue at any time and the basic pairs can be mixed as shown in Figure 2.

Suppose you need a profile of a busy highway. Using COGO routines available in the Construction Five card or your office software, you compute coordinates at the desired intervals on the road and store them in your job file. Using SMI’s stake procedure, you key in the point you want to determine the elevation of and press FSPT, which gives you the horizontal angle and distance to the point. You then turn your gun to the displayed horizontal angle, aim at the centerline mark and press NXT, STOEL. Press enter to overwrite the existing coordinates, and the elevation is stored.

Resection

One of the great benefits of using a data collector, especially for stakeout, is the ability to set the instrument up in any location and shoot two or more existing points. Commonly known as resection, SMI changed its procedure in Version 6 and now call it “2 Point Free Station,” or simply Free Station.1

Although the program works on only two points at a time, multiple points can be included by using any number of pairs. The result of each pair is stored with a unique point number. When all pairs have been completed, the mean of the results of all pairs can be computed. The error of each point as compared to the mean is displayed, and any pair that is outside of an acceptable limit can be discarded. If one is using pairs from an adjusted network, the results will be quite reliable.

Figure 2. Locating remote objects.

Stakeout

SMI makes setting stakes easy for laying out roads, curb and gutter, storm and sanitary lines, and even buildings.

Horizontal alignments (which can have curves), compound curves, reverse curves and spirals, vertical alignments and any templates that describe the cross sectional shape are grouped together in a chain. The number of chains is unlimited, as is the number of templates in a chain. A crew could take to the field with several chains already defined representing different sections of a project. Then all they need to do is to activate the appropriate chain and they are ready to set stakes. The station of any point on the alignment can be determined as well as any offset to any station. The station offset routines work quite well even on closed alignments such as a large parking lot island, a race track or even complex buildings.

When staking stations that have no defined templates, the two adjacent templates are pro-rated, making it possible to stake transition sections and curves with super elevation. Templates, which can have an unlimited number of segments, can be copied and then edited, making it easy to enter data. A much more efficient method, especially for large projects, is to generate the chain data on the computer and transfer it to the HP48 along with any coordinate data.

Figure 3. Building offsets.
I found that when staking offsets where there is a sharp change in direction, such as a building corner, the offset would be referenced to the side after the corner is turned. In order to set an offset stake referencing the side prior to turning the corner, it was necessary to use a station slightly less than the true corner station. For example, 1+94.999 instead of 1+95 as shown in Figure 3. This gave me an offset stake location close enough for practical purposes. I would like to see two buttons instead of one so the user could select the side prior or after the corner point, as appropriate.

SMI uses a “Random Point File” to contain a list of point numbers to represent features of a project such as a boundary, lot description, cross section or a list of points to be staked. When used to represent a boundary, it can be used to compute the area, or to break out portions based on pre-defined areas, or to store a number of points to be staked. When used for a stakeout list, the user merely presses NEXT to get the angle and distance to the next point to be staked.

User Interface

Job files are stored in the HP48 memory if no RAM card is present. I found that the occupied and backsight points as well as the HI and height of rod are not retained with the job, but are global. The values used in the last job are the default when a different job is opened. Since it would be rare that one would change job files while retaining these old values, I would like for these to default to a standard value, such as 0 or 999. I would also like to have a warning provided if they are not properly established.

Transfer 7

SMI has released an updated transfer program. The new program has many improved features, including the ability to select multiple files for transfer to or from the data collector. Transfer 7 will convert SMI data files to the format of a number of other data collectors and software programs.

When transferring files from the data collector, there is an option to store the job as a binary file. This provides an archive copy if needed for court purposes. This file cannot be viewed or printed directly, but can be converted to the SMI or many other standard industry formats.

When transferring jobs between the HP48 and the PC using Transfer 7, the user has the option to select multiple jobs and to select the portion of each job to transfer. When transferring a job, if the file already exists, the user is given the option to replace, rename, store in another location or cancel. This occurs after the file is transferred. I would like to see all the warnings given at the start so one could walk away while the process is taking place.

Documentation

The manual for Version 7 is made up of two major sections. The main section is basically a tutorial, which takes the user through the procedures for a few basic functions. The remainder of the manual consists of six appendices, the first one being a reference section. Others include instrument data, state plane grid constants, a short description of other SMI products, and a glossary.

While most detailed background material can be found in the tutorial section, some appears in appendix A. I would like to see the detailed explanation moved to the tutorial section and the appendices published in a separate manual. This would reduce the size of the manual that field crews would need to carry.

I would like to see a more detailed index. This would make it easier to find things, especially when a user uses a different term. For example, SMI uses the term Multiple Angles for collecting set information. Other terms commonly used for this activity are repetition angles and set collection.

When using the program, the user encounters numerous acronyms such as CAR, STOEL, X PT, and many others which are names of various functions. These shortened function names are necessary because the display space on the HP48 softkeys is limited to five characters. Some were easy for me to figure out, but others were quite difficult. The text includes expanded definitions of some, but it is almost impossible to find the text reference when most of them are not listed in the index. I would like to see the addition of an appendix giving the pronunciation and a description of the function activated by the acronym.

The tutorial takes one through the process of traversing around a parcel consisting of a series of straight lines. All bearings (or azimuths) and distances are provided except the last leg. The user is instructed to determine this one by inversing between the last point computed and first point in the boundary. These values are then keyed in and the closing point is generated. The discussion points out that this point doesn’t match the POB, but it is close2. While some deeds may omit the closing leg by stating something like “and thence back to the point of beginning,” it seems unlikely that a surveyor would use this procedure to close a traverse if there was another way. I would rather see the last leg given and the procedure for determining an inverse discussed separately.

SMI has several videos available, which I found to be quite valuable.

Summary

My real appreciation of Construction Five developed rapidly when I took it to the field. The keystroke sequence needed to accomplish a given task registered quickly. It didn’t take long to realize that the availability of many of the functions discussed earlier were more than a nice thing to have.

I was impressed with the number of functions crammed into the Construction Five card and of the unique solutions that were available to solve surveying problems, like the remote object and Store Elevation functions mentioned earlier. Others include converting feet and inches to decimal feet, and the reverse, a handy function when working with architectural drawings; trig functions that work with degree, minute and second values without the need to convert to decimal degrees; offsets to spirals and the inverse function which shows both ground and grid values if the scale factor has been entered.

Users who are still using version five will find significant changes, which are both convenient and functional. These include the use of alphanumeric identifiers instead of numeric to show that raw data, elevations, notes or the instrument is active. Other changes include the access of more functions from the keyboard, improved screen plots, and the option of using either or both resection points to compute the elevation of the instrument location. Firms who do extensive highway work will find the new combined DOT and SMI overlay convenient.

Firms that are considering a major change in their data collection software will find that SMI deserves serious consideration. While SMI has a strong offering in the HP48 technology, it is also keeping up with modern trends. SMI currently offers surveying software for the TITAN, a Windows CE device. Also, while SMI makes no promises, it is keeping a close watch on other modern developments such as PDA devices and pocket PCs. Whatever platform becomes popular with surveyors in the future, SMI is sure to be there maintaining its support of the surveying industry.

1 The 2 Point Free Station Surveying procedure is based on the system described by Charles Elam in the June 1997 issue of ACSM’s Surveying and Land Information Systems Journal. Volume 57, Number 2, Pages 85-98.

2 While the display precision of distances can be set as high as 11 decimal places and angles to 0.1 second, the defaults are four decimals and to the nearest second. The default display precision displays a rounded distance and angle measurement, which is not exact, however, internal calculations in the calculator are carried out to 11 decimal places.