A 45° angle means the height is the same as the distance away.

The obstacle is 7.8 meters away, so it is 7.8 meters taller than your eyes.

Since your eyes are already 1.8 meters above the ground, add that to the 7.8 meters.

7.8 + 1.8 = 9.6 meters

Answer: The obstacle is 9.6 meters tall.

https://www.omnicalculator.com/math/right-triangle-side-angle

3.16.6.3. Evaluate the DZ route of flight (run-in, drop and escape) to determine if there are obstructions or over-flight restrictions that may affect an aircraft’s ability to achieve drop altitude and airspeed, conduct the drop and safely escape off the DZ. At a minimum, evaluate ingress and egress routes 10 NM from PI. (T-2). If hazards/adverse conditions are identified, the run-in may be modified/restricted for safety reasons, the minimum drop altitude increased, or the safety of flight review denied.

3.16.3.3.2. Open Water DZs. Proposed water DZ locations that do not have land terrain features within 2 NM may be surveyed without a physical inspection.

3.5.2. Airspace Hazards. The existence of instrument flight rules, military training routes,
visual flight rules (VFR), training routes, and slow routes and airway (Victor, Jet, or ICAO equivalent) may be hazardous to aircraft on the run-in or escape course. Document all military training routes, VFR routes, and slow routes within a 10 NM radius of the DZ center point, on block 11, remarks of AF Form 3823. (T-2).

3.3. DZ Criteria. DZ selection factors include (but are not limited to) enemy threats, mission requirements, dispersion, risk of unintended airdrop damage, aircraft capabilities, aircrew capabilities, parachutist capabilities, type of parachutes used, type of equipment to be airdropped, and load or personnel recover-ability. The DZ surface, to the greatest degree possible, should be relatively flat, smooth terrain with no obstacles, vegetation or significant terrain features. If obstacles or other potentially hazardous conditions at the time of survey do exist, the surveyor must identify them on the DZ survey. (T-2). Existing obstacles should be briefed to all personnel prior to use. The ground mission commander and/or Jumpmaster must brief obstacles not listed on the survey and all hazardous conditions to personnel prior to use. (T-2). All airdrops conducted on DZs that do not meet DAF minimum size requirements must have a DZ size waiver in accordance with paragraph 1.4. (T-1).

DAFMAN 13-217, Paragraph 5.5, HLZ Survey Assessments/Updates

5.5. HLZ Survey Assessments/Updates. To ensure survey information is current and remains valid, assess existing HLZ surveys every 12 months. (T-2). If not assessed within 12 months, the HLZ will be closed until an assessment is accomplished.

3.3.7. Circular DZ. The PI of a circular DZ is normally at the DZ center to allow for multiple
run-in headings. For specific missions, the PI location may be adjusted to allow for sequential
HE or mass CDS, on circular DZs. Refer to Figure 3.1, option 2 for PI placement. Utilizing a
PI not at the center of the circular DZ may limit the run-in heading to only one direction. When
dropping mass CDS to a center point PI, aircrews may target the sticks middle bundle to the
center point. The minimum DZ dimensions for the type and number of loads being dropped
must completely fit into the surveyed circular DZs. (T-2). For both types of PI placement, use
Figure 3.1 to determine the number of jumpers per pass.

3.3.2. Tactical DZ. A tactical DZ is a DZ that is approved for use in an abbreviated or expeditious manner primarily intended to support emerging mission requirements during contingencies or exercises. Tactical DZs are normally restricted to exercise or contingency missions supporting resupply and personnel infiltration airdrops (versus proficiency jumps, routine training, etc.). Tactical DZ surveys are processed and approved in an abbreviated manner, do not require an AF Form 3823 to be physically signed, and may be passed electronically and/or verbally. Tactical DZs normally require a physical inspection of the DZ by the ground mission unit and a safety of flight review. However, computer-based mapping tools, imagery analysis, and other standoff tools may be used during exercise or contingency operations when tactical conditions do not permit the ground mission unit to physically occupy the DZ area to collect survey data.

3.5.6. Aerial Power Line Restrictions. Power lines present a significant hazard to jumpers. Personnel can sustain life threatening injuries from electric shock and/or falls from a collapsed canopy. All restrictions apply to aerial power lines operating at 50 kilovolts or greater. Power lines will be documented on both block 11, remarks, and block 10, DZ diagram, of AF Form 3823. (T-3).

also

A4.1.10. Block 10. Provide a legible, to scale diagram of the DZ including all obstacles or prominent features located within the DZ boundaries and 5 NM from DZ center that could affect ground or flight safety. Annotate the distance these items are from the DZ center in block 11 and depict on the DZ diagram, block 10 to include DZ dimensions. Ensure to annotate all charted or observed water hazards and power lines within 1,000 meters of the DZ boundaries (or 1,000 meters of the MFF PI). Diagram shall be oriented true north and indicated with an arrow. (T-1).

Reference: DAFMAN 13-217, A4.1.10

Diagram shall be oriented true north and indicated with an arrow. (T-1).

3.16.3.3. Physical Inspection. The ground surveyor will conduct a physical inspection of the entire proposed DZ surface to identify and evaluate potential hazards. (T-2). Exception: Physical inspection limitations in accordance with paragraph 3.16.3.3.1 and open water DZs in accordance with paragraph 3.16.3.3.2 The surveyor will identify hazards to DZ operations located within 1000 meters/1094 yards of DZ boundary. (T-2).

3.16.1.3. Austere Polar DZ Surveys. Due to the austere and inaccessible nature of Polar Regions, a physical inspection of the DZ may not be possible. For polar operations, a tabletop review of the austere polar DZ performed by 109th Operations Support Squadron Weapons and Tactics (109 OSS/OSK) will be an acceptable alternative to a DZ survey. (T-2).

DAFMAN 13-217, Paragraph 5.5, HLZ Survey Assessments/Updates

If significant changes or obstacles affecting safety are identified during an assessment, the HLZ will be resurveyed. (T-2). Surveys not updated within 24 months require a new AF Form 4303 with reviewer and approval signatures, and no survey will remain valid beyond five years from the original survey date.

DAFMAN 13-217, Attachment 6, A6.1.9, Block 9

A6.1.9. Block 9. Enter HLZ surface conditions (e.g., grass asphalt, fine dust, etc.). Exercise extreme care to document the possibility of brown or white out conditions, blowing grass, or any other flying debris that may restrict visibility or damage aircraft or personnel. Enter other hazards and remarks as required. For tactical HLZ, send hazards at a minimum if they exist.

Reference: DAFMAN 13-217, A4.1.9.6 and A4.1.9.7

A4.1.9.6. Block 9H. Enter the ten-digit MGRS and latitude/longitude coordinates to the nearest one-thousandth minute for each indicated point.

A4.1.9.7. Block 9I. Enter the ten-digit MGRS coordinates referencing datum and spheroid and the WGS84 latitude/longitude coordinates to the nearest one-thousandth minute for each indicated point.

Reference: DAFMAN 13-217, Paragraph 3.16

Until users complete all steps (survey, ground operations approval, safety of flight review and final approval), AF Form 3823 will not be usable and valid. (T-2).

3.3.1.1. DZ water depth will be a minimum of ten feet, and the area must be free of underwater obstructions to that depth. (T-2). The DZ should be free of floating debris, moored craft, protruding boulders, stumps, pilings, or other hazards within 440 yards/400 meters of the DZ center point.

3.16.3.3. Physical Inspection. The ground surveyor will conduct a physical inspection of the entire proposed DZ surface to identify and evaluate potential hazards. (T-2). Exception: Physical inspection limitations in accordance with paragraph 3.16.3.3.1 and open water DZs in accordance with paragraph 3.16.3.3.2 The surveyor will identify hazards to DZ operations located within 1000 meters/1094 yards of DZ boundary. (T-2).
Additional surface area within 5 NM of the planned DZ center point should be evaluated by physical inspection, map study, aerial photography, GPS and/or electronic mapping tools for hazards to airdropped personnel and/or equipment, man-made or natural structures and ground personnel.

RTK stands for Real-Time Kinematic. Real-Time Kinematic (RTK) positioning is based on at least two GNSS/GPS receivers, a base receiver and one or more rover receivers, to provide highly accurate positioning.

Reference: Trimble GNSS Receiver Help

https://help.fieldsystems.trimble.com/r750/position-modes-rtk.htm

Reference: DAFMAN 13-217, Paragraph 3.16.4

The ground operations approval also fulfills the quality check duties in accordance with paragraph 2.3.3. NOTE: Surveyor will not review their own survey. (T-2).

DAFMAN 13-217, paragraph 5.4.1, HLZ Survey Requirements and Responsibilities:

Completing the HLZ survey involves a physical inspection/evaluation of the HLZ, documenting the information on the AF Form 4303, Helicopter Landing Zone Survey (see Attachment 6), a safety of flight review and final approval/disapproval.

Table 3.1. Standard DZ Size Criteria.

Reference: DAFMAN 13-217, Paragraph 3.16

NOTE: DZ surveys expire 5 years from the date surveyed and Chapter 2 applies.

All approved rectangular DZs are random approach DZs unless Block 11 (Remarks) of AF Form 3823 specifically restricts it, or for safety reasons; random approaches may be used if the airdrop profile requirements can be met within the existing confines of the DZ to permit multiple run-in headings to an alternate PI established during mission coordination. Use of a DZ for random approaches does not require a separate survey, but a safety of flight review must be conducted prior to use. (T-2)

“Standard Airdrop Training Bundle (SATB) airdrops conducted on military reservations and/or restricted areas can use standard CDS DZ size criteria.

Reference: DAFMAN 13-217, Table 3.1, Note 5, Page 13.

"3.16.7. Approving Authority Signature. Surveys must be signed by the Group/CC or O-6 equivalent or higher with authority over aviation missions or assets prior to the survey being used for DZ operations. (T-2). Approval authority may be delegated to deputy Group/CC. This approval assures that the safety of flight review is complete and the DZ is considered safe for air operations. The approval authority does not accept the risks or the responsibility of other units utilizing the survey. Approval authority may also be the designated representative who is performing duties as the Group/CC. "

Reference: DAFMAN 13-217, para. 3.16.1.1

Reference Statement: “Office of the Assistant to the Secretary of Defense for Public Affairs ATSD(PA) MAJCOM sponsored parachute demonstration team operations (e.g., ‘Wings of Blue’, ‘Golden Knights’, ‘Leap Frogs’, ‘Para-Commandos’, ‘Black Daggers’, ‘Silver Wings’) do not require a formal DZ survey for public affairs coordinated high altitude low opening precision parachute demonstrations using DAF aircraft.”

Satellites in geostationary orbit (GEO) rotate with the Earth directly above the equator, continuously staying above the same spot.”

Reference: NASA Earth Observatory, Catalog of Earth Satellite Orbits.

Catalog of Earth Satellite Orbits

3.3.3. Military Free Fall (MFF) DZ (including operations utilizing MFF systems in a Double Bag Static Line (DBSL) configuration). The JM will determine the minimum size DZ based on the number of personnel to be dropped, jumper proficiency, parachute system being used, and the prevailing winds. (T-3). For MFF training operations a minimum DZ size of 55 yards/50 meters by 110 yards/100 meters (rectangular) or 55 yards/50 meters radius (circular) is recommended. See paragraph 3.16.1.1 for parachute demonstration DZ.

3.16.3.5. Surveyor Submission. Submit the completed AF Form 3823 for review in accordance with Chapter 2. The surveyor is responsible for the accuracy of the survey data forwarded for review. Other reviewers may add additional information to AF Form 3823. Coordinate changes to surveyor data with surveyor. (T-2).

3.3.1.1. DZ water depth will be a minimum of ten feet, and the area must be free of underwater obstructions to that depth. (T-2). The DZ should be free of floating debris, moored craft, protruding boulders, stumps, pilings, or other hazards within 440 yards/400 meters of the DZ center point.

NOAA’s National Geodetic Survey defines DOP as an indicator of the geometrical strength of the GPS satellite constellation used for a position and time solution. The U.S. government’s GPS performance analysis also states that DOP measures the geometric diversity of the satellite observations.

https://www.ngs.noaa.gov/PUBS_LIB/NGSRealTimeUserGuidelines.v2.0.pdf

https://oceanservice.noaa.gov/education/tutorial_geodesy/geo09_gps.html

It takes four GPS satellites to calculate a precise location on the Earth using the Global Positioning System: three to determine a position on the Earth, and one to adjust for the error in the receiver's clock.

The minimum number of satellites required to calculate a 3-dimensional GPS coordinate location (latitude, longitude, and altitude) is four.

1. Three Satellites for Position: The first three satellites provide the basic coordinates (latitude, longitude, and altitude) by trilateration, which involves calculating the intersection of three spheres centered around each satellite.
2. Fourth Satellite for Time Correction: The fourth satellite is necessary to correct for any discrepancies in the GPS receiver’s clock. GPS systems rely on highly accurate time measurements, and the fourth satellite helps ensure precise synchronization, removing any timing errors.

BY ORDER OF THE SECRETARY OF THE AIR FORCE
DEPARTMENT OF THE AIR FORCE MANUAL 13-217
22 APRIL 2021
Incorporating Change 1, 19 APRIL 2022
Nuclear, Space, Missile, or Command and Control
DROP ZONE, LANDING ZONE, AND HELICOPTER LANDING ZONE OPERATIONS
COMPLIANCE WITH THIS PUBLICATION IS MANDATORY