Intersections and areas of conflict should then be calculated by solving triangles. Areas may be calculated using double meridian distances, but intersections should never be calculated by forcing a closure. Intersections may be checked by closure. A special situation exists where a former survey excluded an unsurveyed location from the patent and the unsurveyed location has subsequently been abandoned. This area is designated as a tract and its boundaries are determined from the prior survey. See Tract A of the Jim Dandy Lode described in the specimen field notes and plat of the Manual of Surveying Instructions. Another use of a tract is for the purpose of excluding a small area surrounding the discovery of another location not embraced in the survey. Intersections and areas of conflict with patented lands containing mineral rights must also be calculated. Supporting calculation sheets need not be furnished the Bureau of Land Management but computer tapes, if available, will be helpful. The BLM can perform the necessary checks by computer. =5–9= Preliminary Plat: The mineral surveyor will find it advantageous to prepare preliminary plats prior to writing the field notes. One plat should provide the base and give all the details of the survey with items of topography and culture secondary. This plat may be prepared in pencil or ink at the option of the mineral surveyor. It should be such that legible blue lines copies can be furnished to the Bureau of Land Management along with the notes, and to the claimant. It should clearly state that it is a PRELIMINARY PLAT SUBJECT TO CORRECTION. Some offices of the Bureau of Land Management may request a reproducible copy. Plats on linen are no longer required. A secondary plat showing the topography and culture in detail will be an aid in writing field notes, but is not required by the BLM. If drill holes are part of the improvements and are too numerous to show on the base plat, a separate plat is advisable. =5–10= Field Notes: A detailed set of specimen field notes is contained in the Manual of Surveying Instructions which should be followed for form and content. There are, however, some inconsistencies: The title page shown in the manual should not be used. Use current Form 3400–11, as supplied by the Bureau of Land Management. The locations should be listed in the same order that they are described in the field notes, thereby serving as an index. The field notes begin with a description of instruments and the mean results of the solar or other azimuthal observations. The latitude and longitude of the observing station is given. If this is not at a corner of the survey, the latitude and longitude of the first corner described should be given, thus: At Cor. No. 1 of the Jim Dandy lode, identical with Cor. No. 1 of the Prince Lode of this survey, in latitude 38°45′ N, and longitude 106°20′ W.