features  or  works  of  man  to  be  shown,  the  entire drawing  is  in  black  ink.  When,  as  shown  in  figure 10-35, the features other than the survey lines are quite extensive, color printing is used. Survey lines, numbers, lettering, and railroads are printed in black; topographic  relief,  roads,  highways,  trails,  culture, alkali  flats,  sandy-bottom  draws,  and  sand  dunes  are shown in brown; rivers, lakes, streams, and marshes are  shown  by  conventional  symbols  in  blue;  and timbered areas are indicated in green. Where such a green  overprint  might  obscure  other  details,  the presence of timber may be indicated in a note (fig. 10-35).  These  several  colors  are  not  shown  on  the reproduction  of  the  plat  presented  in  figure  10-35, although  the  various  features  are  indicated  in appropriate  colors  on  the  original  map  from  which this  figure  was  reproduced. A  property  plat  plan  must  contain  the  following: 1.  Directional  orientation,  usually  indicated  by  a north  arrow. 2. Bearing and distance of each boundary. 3.  Corner  monuments. 4. Names of adjacent owners, inscribed in areas of their  property  shown. 5.  Departing  property  lines.  A  departing  property line  is  one  that  runs  from  a  point  on  one  of  the boundaries  of  the  surveyed  lot  through  adjacent property.  It  constitutes  a  boundary  between  areas belonging to two adjacent owners, 6. Names of any natural monuments that appear on the plat (such as the name of a stream), or the character of any natural monuments (such as “10-inch oak tree”) that have no names. 7.  Title  block,  showing  name  of  owner,  location  of property, name of surveyor, date of survey, scale of plat, and any other relevant data. The preceding items are those that usually appear on any plat. Some land surveyors add some or all of the following as well: 1. Grid lines or ticks (a grid tick is a marginal segment of a grid line, the remainder of the line between the  marginal  ticks  being  omitted),  when  determinable. 2. On a plat on which grid lines or ticks are shown, comer locations by grid plane coordinates. 3. Streams, roads, wooded areas, and other natural features,   whether   or   not   they   serve   as   natural monuments. 4.  Surveyor’s  certificate.  This  is  a  statement (required by law in many states) in which the surveyor makes a personal affidavit as to the accuracy of the survey, A typical certificate might read as follows: I, (surveyor’s name), registered land surveyor, hereby certify  that  this  plat  accurately  shows  property  of (owner’s name), as acquired in Deed Book 60, page 75, of the land record of (named) County, State of (name). 5. The area of the property. LAND SURVEY PRECISION Most land surveying of tracts of ordinary size is done by using transit-tape methods. For a large tract, however (such as a large government reservation), comers  might  be  located  by  triangulation,  or  primary horizontal  control  might  be  by  triangulation  and secondary  control  by  supplementary  traversing. The  precision  used  for  land  surveying  varies directly with the value of the land and also with such circumstances as whether or not important structures will  be  erected  adjacent  to  the  property  lines. Obviously,  a  tract  in  lower  Manhattan,  New  York (where land may sell for more than ||content|| million per acre),  would  be  surveyed  with  considerably  higher precision than would a rural tract. Again  there  are  no  hard-and-fast  rules.  However, the  prescribed  order  of  precision  for  surveying  the boundaries  of  a  naval  station  might  require  the following: 1.  Plumb  bobs  used  for  alignment  and  for transferring chained distances to the ground 2. Tape leveled by a Locke level 3. Tension applied by spring balance 4.  Temperature  correction  made 5. Angles turned four times If  you  turn  angles  four  times  with  a  1-minute transit, you are measuring angles to approximately the nearest  15  seconds.  The  equivalent  precision  for distance  measurement  would  be  measurement  to  the nearest 0.01 foot. Four-time angles might be precise enough for lines up to 500.00 feet long. For longer lines,   a   higher   angular   precision   (obtained   by repeating six or eight times) might be advisable. 10-36