LOCATING SAMPLE POINTS IN THE FIELD 



The field crew located points on stream- 

 banks that coincided approximately with the 

 sample points marked on the aerial photos.^ 

 After initial training, field crews easily lo- 

 cated each point within — 200 feet by com- 



J Although it is possible technically to locate exact 

 points, such rpjinement is not necessary: if points are 

 to be established as permanent samples, greater pre- 

 cision in matching field points uith those marked 

 on the photos uould be required. In addition it would 

 be necessary to identify the exact sample point by 

 using reference stakes or tree blazes. 



paring photo images with ground details. 

 Possible bias on the part of the field crew 

 in locating the sample point was eliminated 

 by having the crews establish transects 

 exactly one hundred feet upstream from the 

 point first identified on the ground. 



This was done in an effort to minimize the pos- 

 sibility that field crews might allow local conditions 

 to influence the establishment of .sample points, 

 based on the assumption that they could not see 

 (and thus prejudge j conditions one hundred feet 

 away. 



CHARACTERISTICS MEASURED 



Measurements were taken only on those 

 portions of stream channels averaging more 

 than 4 feet wide. Altogether 290 potential 

 transects were located and inspected in the 

 field. Of these, however, only 257 actually 

 were measured because 19 occurred at points 

 where the channel was either dry or too nar- 

 row and 14 fell in extensive beaver pond 

 areas, where wading was hazardous. 



Measurements were made along a transect 

 across the stream at a 90-degree angle to its 

 centerline (fig. 3). If more than one channel 

 was found, the transect was extended to the 

 bank of the second channel . This process 

 was repeated until all channels of a stream 

 had been crossed. All measurements were 

 recorded on the form shown in figure 4 . 



STREAM BANK 



Figure 3. — Point .\ in above drawing represents the point identified by the 

 field crew as approximating the location of the sample point shown uu aerial photo. 

 Point B was then established 100 feet upstream as one end of transect. 



4 



