Research Noti

SO-257

Data Recorders Speed Forest Surveys’

George C. Keith and Roy C. Beltz

SUMMARY

Adapting computer and communications concepts to conduct and analyze forest surveys has

been undertaken by the Renewable Resources

Evaluation Research project of Southern Forest

Experiment Station. How data is relayed from the

faraway forest site to the unit’s base without handwriting one note is described in this study.

Additional keywords: Forest inventory, data capture, telecommunications, data editing and processing, ADP, computer processing.

INTRODUCTlON

Forest survey field teams have been cruising

plots and writing numbers on tally sheets since

1933. At last, a feasible alternative is available

and advancing technology is reducing equipment

costs of that alternative. This report describes

use of portable data recorders in the Renewable

Resources Evaluation Research (RRE) project of

Southern Forest Experiment Station.

BACKGROUND

The Renewable Resources Evaluation Research

project of the Southern Station is responsible for

surveying forest resources in the Midsouth -Alabama, Arkansas, Louisiana, Mississippi, Oklahoma, Tennessee, and Texas. The project constantly remeasures some 26,000 permanent forest

plots, each being covered at nearly lo-year intervals. Great quantities of data are generated and

must be reduced to tables for analysis and interpretation. And data will increase substantially as

RRE units respond to the Resources Planning Act

of 1974 and collect ,information about the nontimber resources.

Although RRE units have sought more efficient

ways to deal with the flow of information, virtually

all data has continued to go onto tally sheets and

then be coded into punch cards. Such cards and

accounting machines to “read” them were put

into use in the late fifties.

Southern Station RRE shifted to computer processing in the early .axties. Additional progress

has come slowly. Until 1976, RRE jobs were submitted via messenger to a remote host computer

center. Printed results were obtained the same

way. In 1976, the RRE unit installed a group of

devices that permitted telecommunications with a

host processor and also provided some local computing capability.

The components included a programmable desk

top calculator, card reader, printer, and plotter.

A disc system was added later to store files and

programs. A terminal with dual tape cartridges

and another printer were added in 1977 to complete the present hardware.

A perennial problem has been the process of

editing tally sheets, punching data cards, and the

IUse of trade, firm, or corporation names is for the reader’s

information and convenience. Such use does not constitute

official endorsement or approval by the U.S. Department of

Agriculture to the exclusion of any other suitable product.

Southern Forest Experiment Station/T-10210 US. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi, Eastern Oklahoma, Tennessee, Eastern Texas.
screening for errors introduced by the field cruisers, by misinterpretation of handwritten codes, or

by keypunching mistakes. These tally sheets go

wherever the plots are, and are exposed to water

and insects. All these factors detract from the

fidelity and integrity of the resource information.

FIRE has investigated several alternatives to

tally sheets. Tape recorders and portable card

punchers were tried and discarded. The development of data recorders, digital entry models with

tape transport, and the solid state memory units

led to RRE experiments with the MSV77 data

recorder in 1978. This unit passed tests and

adaptations. About half of Southern Station RRE

plot information is entered in recorders carried

by staff members in the woods and is transmitted

via telephone to base facilities in New Orleans.

time, recording an initial set (A) of information on

each of them. Next, A must be entered for all new

trees. Recorded data eventually arrives in a long

character string with identifiers or signposts for

state, county, plot, and sample point. Several trees

are commonly recorded at each point so set A

is identified by a signpost record denoting point

and tree. (FFl 01 for point 1 tree 1). All subsequent

data up to the next signpost belong to set A of

point 1 tree 1.

Data recorders were designed for special inventory needs of supermarkets and warehouses where

stock numbers and quantities comprise no more

than 12 digits. But RRE researchers operate in

terms of 80-column tally sheets, a holdover from

days when data was synonymous with punch

cards. Experienced cruisers are accustomed to

the sheets and can tell at a glance if they have

completed all the required items. This posed the

problem of how to squeeze the 80-column format

into the 12 characters displayed on the data

recorder.

When set A is completed for the first tree, a

second signpost denotes the next tree (FF102).

Once all trees have set A completed, signpost

(FFlOl) is used again to denote the set B of

tree 1 on point 1. Set B is then completed for

all trees. The 34 subscripts provide unique reference to each item between signposts and are

recorded as field entries. Each record, like the

signpost, is a B-digit number including a P-digit

code for the subscript and a 3-digit code for the

variable. Each entry will automatically be followed

by the delimeter “ + ‘I. A typical example of pointtree information after being recorded and transmitted will appear as:

FFl 01 + 50144 + 51010 + 53001 + 55011 +

FF102+50030+51001 + . . . . ..a

The Southern Station FIRE answer was to use

subscripting. The concept of subscripting variables and recording 1 per record is the key to

using the small display for expansive records.

Cruisers normally record their information in

numerical form by using codes for items such as

crown class, species, and log grade. Through

constant use, these codes become second nature

to the cruisers. At the present time the number of

items recorded on a sample tree ranges from 8 to

34, depending upon the size and quality of the

tree. To use data recorders, cruisers must additionally, 1) memorize the subscripts for the 34

items, and 2) record information in a systematic

or checklist fashion to ensure notation of ail required items.

In this case, FFlOl, which is point 1 tree 1, is

followed by the field entry 50144 + (which includes-the P-digit subscript), 50 referring to the

variable “azimuth”‘with a 3-digit value of 144, the

“ + ” denotes the end of the short record and will

be automatically inserted after each field entry

item when transmitting the data. Subsequent

entries of 51010, 53001, and 55011 are included

in point 1 tree 1.

Utilizing the checklist, which was developed

after observing experienced crews operate in the

field, the procedure change from tally sheets to

data recorders was minimized.

Basically, the routine requires a cruiser, first,

to account for all previously tallied trees, one at a

FF102 then follows. This signifies point 1 tree 2.

It identifies the next tree within the point and is

followed by its respective subscripted variables.

Zeroing of subscripted variables with null fields

is not required. Thus, record length may vary

from 1 entry to more than 80 characters: and one

may dispense with the magic “80 columns”.

Actually, the subscripting of variables between

signposts could allow random order data entry,

if cruisers could remember which items have been

entered or not entered.

Although some drawbacks are evident, they are

eclipsed by the advantages. Most losses in efficiency stem from the inability to deal with more

.- _ Keith is a computer programmer and Beltz Is a researcn torester and project leader, Southern Forest Experiment Station, Forest

Service - USDA, New Orleans, Louisiana.

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than one tree at a time. Adjacent trees may be

tallied simultaneously under the old scheme.

Heights are measured by hysometer used at a

known distance from the tree. Thus, adjacent trees

can be “shot” from the same point. Eliminating

this flexibility causes some consternation for the

cruisers, but we expect several benefits to accrue.

One benefit is removal of the tendency for cruisers

recording two trees at one time to get the observations swapped.

An advantage is that the use of a checklist

makes it easier to train new cruisers and tends

to reduce omissions of required items. Cruisers

benefit by having prompt feedback on their recording errors. In this way, errors may be corrected before they become habitual. Some cruisers claim that data entry is faster and easier with

the data recorder than with the tally sheet.

On the computing side, the advantages are

much more concrete and drawbacks are few.

Visual editing of tally sheets and key punching

are eliminated. So are the additional errors they

introduce. Checking a plot’s data as it is received

can be automated, as can progress reports and a

host of other reports. With tally sheets and card

punching, one month could lapse between plot

measurement and an editing report to the cruiser.

With data recorders, it is possible to complete

the editing in a few minutes. In practice this can

be accomplished overnight.

The data recorders currently used have a

16,000~character memory capacity. This will ordinarily hold plot data measured over 3 to 4 days.

Storing much larger data sets in recorders is technically feasible. In remote locations, up to 3 weeks

of information could be stored before transmission. In general however, the risk of losing data

sets through physical abuse of the recorder must

be weighed against the price of a phone call.

Recorders can be damaged by physical abuse

such as dropping and by immersion in water. In

addition, storing data for extensive periods defeats the advantages of quicker response to field

errors. Southern Station personnel prefer to transmit information when the recorders are two-thirds

to three-quarters full. This allows a buffer, so that,

if transmission is impossible, the cruiser can enter

more data and transmit later.

Efforts are aimed at minimizing risk of information loss. To date, transmission of information

has suffered little difficulty. Two units did not work

when received initially, but were promptly repaired.

One failure has occurred, but no information was

lost. The greatest risk will come from dropping,

immersion, or other abuse of the recorders. This

risk is minimized by having conscientious personnel and by regarding data’ recorder? as an advantage - not a burden.

A small acoustic coupler, compatible with the

Bell 202s modem, quickly and easily upgrades

the data recorder to a portable data terminal.

Data is transmitted over the public-switched network at a transmission speed of 1200 bps (bits

per second). Transmission mode is asynchrdnous

using a half duplex protocol.

Communications to date have been excellent

with data transmitted daily to headquarters from

any of seven States. Data integrity is insured by

sending two sets of data, which are received on

separate tape drives. A comparing feature of the

HP2645 CRT terminal then insures that no characters have been altered during transmission by

checking character against character, one drive

against the other. Transmission errors are few

and easily corrected.

After the coded data is received and the tape

cartridges are edited on the CRT, it is logged

according to field crew leaders and stored on

hard disc cartridges. Data is then edited by the

project’s HP9830 computer system using unique

codes in respect to plot, point, and tree variables.

At this point, card images are generated to serve

as input to the project’s standard editing program

which checks field data for logical errors. Cruiser

errors are then detected and-quickly sent back to

the field crew leaders. This procedure not only

helps to correct recent errors but also alerts cruisers to potentially recurrent errors in successive

plots. An interactive program developed for use

with the HP9830 system allows the CRT to update

disc records easily at any stage of the data set,

(including the original coded data file or the card

image file). After edits are completed, ,the final

version of the card image file is transmitted to the

project’s host processor, a UNIVAC 1108, which

processes the balance of the computer workload.

Although operations run smoothly under the

present arrangements, RRE intends to upgrade

the present data acquisition system. The latest

MSI models sell for one-third less than our models, possess the ability of partitioning memory into

distinct sections or pages, and will soon be offered

with LCD (liquid crystal display), which is much

easier to see in the sunlight. Further communications capability will improve to the point where

error-checking mechanisms are built into the communications protocol. This will allow data recorder

transmissions to be automatically received and

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verified without operator intervention.

Eventually portable work stations will be placed

in the field for each field group leader; who will

be responsible for collection of crew data, prs

editing, and final transmission of data to headquarters. This concept would contribute significantly to a more systematic and organized flow

of data both from and to the field. Sophisticated

hardware can be implemented at nominal cost

and each field leader could keep cruisers abreast

of any current data collection problems.

CONCLUSION

Data recorders offer several advantages over

conventional tally sheets and punched cards. By

subscripting variables and using signposts, logical record length may be varied at will. Data entry

is easier, sources of human errors are minimized,

and time between data capture and processing is

cut drastically. Additional benefits that are probable but not. yet substantiated include reduced

cost, faster data entry, and easier training for

new cruisers.

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it U. S. GOVERNMENT PRINTING OFFICE: 1980-672-510~8