Data Filtering 



The third value in the second column of Table 7-2, is an order of magni- 

 tude greater than the neighboring values. It is not sensible that the concentra- 

 tion should increase by an order of magnitude and then decrease by the same 

 in two-tenths of a second. This is even less realistic considering the behavior 

 of the surrounding data, as well as the corresponding data from the other sen- 

 sors. In Table 7-3, this point has been replaced with a value interpolated 

 from the neighboring data. Figure 7-4 graphically presents the filtered 

 version of the 15-sec segment of data presented in Figure 7-3. The 1-sec seg- 

 ment of data presented in Table 7-3 is contained within this larger segment. 



Table 7-3 



Sample of Converted, Filtered Data 



Time, sec 



C.glt 



AAA 



BBB 



ccc 



DDD 



EEE 



53070.0 



3.9550 



2.8584 



3.5655 



2.8349 



2.8472 



53070.1 



4.4216 



4.2038 



3.1923 



2.8602 



2.0022 



53070.2 



3.5847 



4.5529 



4.5344 



1.6225 



1.1904 



53070.3 



5.0068 



3.0332 



4.4030 



1.6577 



1 .7500 



53070.4 



3.4773 



2.6959 



2.5800 



2.1973 



1 .3543 



53070.5 



2.9845 



2.7767 



2.5691 



1.9870 



1.4331 



53070.6 



2.9830 



2.8585 



2.9539 



2.8800 



1.5926 



53070.7 



2.9830 



2.4492 



2.4126 



2.7534 



1.5130 



53070.8 



2.5000 



2.8571 



2.5672 



2.4278 



1.4331 



53070.9 



3.4579 



3.9047 



2.9483 



3.5656 



2.1172 



Summary of data characteristics 



Each of the data files for the mobile OBS array has an associated ledger 

 file which contains run information, statistics, and sensor positions. Table 7-4 

 is a sample ledger file for Run A1314AOB and contains information about the 

 converted, filtered file presented above. 



The first line of the ledger file identifies the run and is followed by the 

 SUPERTANK test number, wave generator file, and a short description of the 

 test. Test conditions are presented in the second section of the ledger file. 

 Design wave heights ranged from 0.2 to 1 m and the periods ranged between 

 3 and 10 sec for both random and regular wave conditions. Start and stop 

 times found in the ledger file provide the interval of wave generation during 

 which the OBS sensors were collecting data. This is the segment of data used 

 to determine concentration statistics. 



Instrument positions were measured in feet from the channel origin. 

 English Units were chosen as the convention because the wave channel was 

 originally designed using this system. The mean and standard deviation for 



Chapter 7 Sediment Suspension Measurements from a Platform 



131 



