CASA 32/97 - Determination under paragraph 178(1)(b) of the Civil Aviation Regulations

The Determination introduces a compact set of interlocking technical concepts that together determine which terrain or obstacle datapoints are captured and how an LSALT is computed. The core defined concepts are:

• LSALT (Lowest Safe Altitude): the altitude being determined; the instrument prescribes how to compute it when a statutory determination under paragraph 178(1)(a) is absent (para 2.1-2.2).

• Grid LSALT: the LSALT value shown for a grid square on an En Route Chart (ERC) or Terminal Area Chart (TAC). The Grid-LSALT pathway uses published chart grid values rather than raw terrain/obstacle data (definition in schedule).

• Effective area: the geographic area whose terrain and obstacle information feed into the LSALT calculation. It is defined differently depending on whether Grid LSALTs are used. If Grid LSALTs are used, the effective area is "the area of the earth’s surface represented by all the grid squares over which the navigation tolerance area determined in accordance with paragraph 5.1 is shown to extend wholly or in part" (para 3.1). If Grid LSALTs are not used, the effective area comprises the navigation tolerance area plus a 5-mile surrounding zone (para 3.2(a)-(b)).

• Navigation tolerance area: a band around the planned track representing the area within which navigation error must be tolerated. Two definitions are provided. If LSALT determination is by reference to Grid LSALTs, the navigation tolerance area is "ascertained by applying on either side of the planned track the navigation error allowance appropriate to the navigation aids, system or method used" (para 5.1). If not, the navigation tolerance area is constructed geometrically by diverging lines from the start of the segment at prescribed angles (10.3° if a navigation aid is used at the start, 15° if not) and then continued subject to further rules that depend on whether an area navigation system is used, where lines reach points abeam the end of the segment, distance limits (30 or 50 miles), and the rated coverage of the navigation aid at the end of the segment (para 5.2). The rules are prescriptive and layered (paras 5.2(a)-(f)).

• Corrected highest terrain: when an aeronautical topographical chart is used to calculate LSALT, the instrument defines "corrected highest terrain" as the higher of (a) the highest spot height in the effective area plus 360 feet, or (b) the height of the highest contour shown plus the contour interval plus 360 feet (para 4.1). That is, the Determination explicitly builds a 360-foot padding above charted terrain features and treats contour intervals sensitively by adding the contour interval to the highest contour.

• Rated coverage of navigational aids: for VOR-served segments, "rated coverage" is taken to be 60 miles or the coverage published in ERSA for the route segment, whichever is less (para 5.3). The term "rated coverage" is used to limit how far the navigation tolerance geometry will extend when lines seek points within the navigation aid's coverage area (paras 5.2(b)-(d)).

Other technical points: the instrument sets a floor of 1,500 feet above mean sea level (para 2.1(c)), prescribes upward rounding to the next 100 feet for the non-Grid pathway (para 2.1), and explicitly ties the Grid-LSALT pathway to charted ERC/TAC products (para 3.1 and defn of Grid LSALT). The geometry uses precise divergence angles (10.3° and 15°) and prescribes semicircles of defined radii (30 or 50 miles) or continuation to rated coverage points dependent on whether area navigation is used (para 5.2). Together, these concepts determine the spatial envelope and the maximum terrain/obstacle datum that must be considered for any LSALT calculation.

The Determination governs any person or body that is called upon to determine an LSALT for a route segment in circumstances where an LSALT has not already been determined under paragraph 178(1)(a) of the Civil Aviation Regulations. The instrument itself is made by a CASA delegate (signed by the General Manager, Flying Operations Branch), which indicates that it is a regulatory tool provided to set the calculation methodology available to regulators, flight-planning authorities, and chart compilers (first page). The immediate practical stakeholders identifiable from the text are:

• Those conducting LSALT determinations: the instrument applies to the act of determining LSALT under paragraph 178(1)(b); it establishes the method that must be used in such determinations (first page; para 2.1-2.2). The Determination therefore affects whoever, under the regulatory framework, has responsibility to produce or certify LSALTs for route segments not already covered by paragraph 178(1)(a).

• Aeronautical chart publishers and chart users: Grid LSALTs are taken from En Route Charts (ERC) and Terminal Area Charts (TAC) (definition of Grid LSALT; para 3.1). The instrument will affect how charted grid LSALTs are used in calculations and therefore the use and interpretation of ERC/TAC products.

• Flight planners and operators: the calculation rules define the altitude that is the LSALT for a given route segment. Operators and flight planners who must plan routes or file flight plans with awareness of LSALTs will be affected insofar as they must respect the altitudes determined under this method.

• Pilots and flight crews: although the Determination does not directly prescribe crew conduct, it produces the numerical LSALTs that will appear on charts or operational documents and that pilots will use for safety margins; thus pilots will use LSALTs produced in accordance with this Determination.

• Aeronautical data providers: the method requires specific data inputs,highest reported obstacle in the effective area, spot heights and contours from aeronautical topographical charts, Grid LSALTs on ERC/TAC, and VOR coverage as published in ERSA (paras 2.1(a), 4.1, 3.1, 5.3). Entities that maintain or publish those data sets are implicated because their published values feed directly into the calculation.

• Organisations planning navigation systems and choosing navigation methods: the navigation tolerance area (and therefore the effective area) depends on whether navigation aids are used at the beginning or end of a segment, whether an area navigation system is being used, and the rated coverage of aids (para 5.1-5.3). That means operational choices about navigation method feed back into the LSALT determination.

Finally, the Determination explicitly revokes an earlier instrument (SRS 2/1992) (first page, para 1(a)). Any organisation that had relied on SRS 2/1992 for its procedures will therefore need to adopt the method set out in this Determination for subsequent LSALT determinations.

The Determination imposes procedural duties in a narrow technical sense: it obliges the person performing an LSALT determination under paragraph 178(1)(b) to apply the prescribed method. The duties and entitlements, as expressed in the instrument, include the following, with the relevant provisions cited.

Duties

• Apply the specified calculation method where an LSALT has not been determined under paragraph 178(1)(a). The Determination states the method in clear alternative pathways (paras 2.1-2.2).

• When applying the non-Grid pathway, compute three candidate altitudes and select the highest: (a) 1,000 feet above the top of the highest reported obstacle in the effective area; (b) if an aeronautical topographical chart is used, 1,000 feet above corrected highest terrain in the effective area; and (c) 1,500 feet above mean sea level (para 2.1). After selecting the highest, round upward to the next 100 feet (para 2.1).

• When applying the Grid-LSALT pathway, identify the effective area in terms of grid squares that are overlapped wholly or in part by the navigation tolerance area and select the highest Grid LSALT shown for those grid squares (paras 2.2 and 3.1).

• Compute the effective area: if using the Grid-LSALT pathway, the effective area is composed of grid squares over which the navigation tolerance area determined under para 5.1 extends wholly or in part (para 3.1); otherwise the effective area is the navigation tolerance area determined under para 5.2 plus a 5-mile surrounding zone (para 3.2).

• Construct the navigation tolerance area. Either apply the navigation error allowances appropriate to the navigation aids, system or method used and project those allowances on either side of the planned track (para 5.1), or, where para 5.1 does not apply, use the geometric rules in para 5.2 (diverging lines at specific angles, distance limits, semicircles, and interaction with the rated coverage of navigation aids).

• When using an aeronautical topographical chart, compute the corrected highest terrain as the higher of highest spot height plus 360 feet or highest contour height plus contour interval plus 360 feet (para 4.1).

• For route segments served by a VOR, apply a limit to rated coverage: use 60 miles or the ERSA-published coverage for the segment, whichever is less (para 5.3).

Entitlements / Structural provisions

• Use of Grid LSALTs: where the LSALT determination is to be made by reference to Grid LSALTs shown on ERC or TAC, the instrument entitles the determiner to adopt the highest Grid LSALT for the effective area as the LSALT (para 2.2). The instrument thus provides an alternative, chart-based procedure that can be relied on where those chart values are used.

• Use of aeronautical topographical charts: the instrument allows the use of aeronautical topographical charts as the basis for calculating corrected highest terrain and thus LSALT under the non-Grid pathway (para 2.1(b) and para 4.1).

• Predictability via prescriptive geometry: because the navigation tolerance area and effective area are prescribed in geometric terms (angles, miles, semicircles, rated coverage limits), the instrument provides deterministic guidance that can be replicated by those performing the calculation (paras 5.1-5.3 and 3.1-3.2).

Limitations

• The Determination does not itself create or list penalties, nor does it purport to alter the statutory powers in the Civil Aviation Act or Regulations; it functions as a method-determination under paragraph 178(1)(b) (first page). It therefore imposes a technical obligation on the act of LSALT calculation, but it does not, within its own text, set out enforcement mechanisms or civil/criminal sanctions.

In short, the primary duty is procedural and computational: when an LSALT must be determined under the relevant regulatory provision, the determiner must follow the stepwise method laid out in the Determination, choosing the Grid-LSALT route where appropriate and otherwise following the non-Grid pathway including the specified rounding and padding rules.

The Determination itself does not specify offences, penalties or enforcement mechanisms. It is expressly a Determination under paragraph 178(1)(b) of the Civil Aviation Regulations and contains only procedural and definitional material that prescribes how LSALT is to be calculated (first page; schedule). The text contains no clauses that create monetary fines, imprisonment, administrative sanctions, or explicit enforcement steps.

Because the Determination is made under the Civil Aviation Regulations framework (as stated on the face of the instrument), any enforcement or contravention consequences that arise from failure to apply the prescribed method will be a function of the Civil Aviation Act 1988 and the Civil Aviation Regulations and the enforcement architecture established by those instruments. The Determination does not itself restate or modify that enforcement architecture.

Practical implications from the text

• The Determination functions as a mandatory method where the Regulations require an LSALT to be determined under paragraph 178(1)(b). Failure to follow the Determination when performing such a regulatory act would be a failure to apply the method prescribed by CASA under its delegated power. The Determination does not, however, set out what sanctions would follow; those would need to be located in the Act or Regulations rather than in this instrument.

• Because the instrument relies on external data sources (ERC, TAC, aeronautical topographical charts, ERSA for VOR coverage), enforcement of correct application necessarily depends on those inputs being available and accurate. The Determination itself does not address data quality, data update frequency, or who is obliged to publish or maintain the underlying data sets.

• The instrument revokes the earlier SRS 2/1992 (first page; para 1(a)). Any enforcement considerations with respect to actions taken under SRS 2/1992 prior to revocation are not addressed here.

In summary, the Determination prescribes calculation mechanics but does not, in its text, create a bespoke enforcement regime or list penalties. Any enforcement against a person or entity for failure to comply with the method will be effected through the statutory enforcement mechanisms of the Civil Aviation Act and Regulations, and those mechanisms are not restated in this instrument.

The Determination situates itself explicitly within the Civil Aviation regulatory architecture. It is made under paragraph 178(1)(b) of the Civil Aviation Regulations and therefore operates as a subsidiary instrument deriving authority from the Regulations and, by extension, the Civil Aviation Act 1988 (instrument heading and first page). The ways in which it interacts with other legal and regulatory sources, as evident from its text, are as follows:

• Supersession / revocation: the Determination expressly revokes instrument number SRS 2/1992 (first page, para 1(a)). That revocation changes the body of subsidiary instruments that apply to LSALT calculations and substitutes the method in this Determination. The instrument therefore functions as an update to the regulatory method-set for LSALT where the Regulations require a method.

• Dependency on Civil Aviation Regulations: the Determination repeatedly references the split between determinations made under paragraph 178(1)(a) and determinations made under paragraph 178(1)(b) of the Civil Aviation Regulations (first page; para 2.1-2.2). It applies only where the LSALT "has not been determined under paragraph 178(1)(a)" and therefore interacts with the procedural division of responsibility and the legal effects established in the Regulations.

• Reliance on chart and aeronautical publications: the method is defined to incorporate values published on En Route Charts (ERC) and Terminal Area Charts (TAC) through the Grid LSALT concept, and it refers to ERSA for published VOR coverage (definition of Grid LSALT; paras 3.1 and 5.3). That produces a cross-reference to the body of aeronautical publications that are part of the safety information ecosystem. The Determination therefore relies on, and implicitly defers to, the published content of these instruments for some inputs into an LSALT computation. The Determination does not itself publish grid values or ERSA data: it prescribes how such published values are to be used.

• Relationship with operational navigation practice: the navigation tolerance area can be ascertained by "applying on either side of the planned track the navigation error allowance appropriate to the navigation aids, system or method used" (para 5.1). This cross-references operational standards and navigation equipment performance. The Determination interacts with the standards and performance characteristics of navigation aids and area navigation systems, although it does not redefine them.

• Technical interplay with aeronautical charting standards: the construction of corrected highest terrain requires knowledge of spot heights, contours and contour intervals on aeronautical topographical charts (para 4.1). Thus the Determination operates in tandem with charting conventions and the specification of what constitutes an "aeronautical topographical chart". The instrument does not itself define chart publication standards, but it presumes their existence and that the determiners will be able to extract spot heights and contour intervals from those charts.

• Non-substantive interaction with enforcement law: as noted, the Determination does not set penalties or enforcement steps. Consequently, its legal bite depends on the enforcement architecture in the enabling legislation and regulations. The Determination interacts with other legal instruments to the extent that those instruments impose obligations or sanctions regarding compliance with CASA determinations or with LSALT requirements generally.

Taken together, the Determination is a procedural, technical instrument that integrates with charting publications and navigation-system characteristics and sits within the Civil Aviation statutory/regulatory framework. It revokes a predecessor instrument and thereby changes the body of subsidiary rules that apply to LSALT calculations.

The Determination itself records a single, discrete amendment action: it revokes instrument number SRS 2/1992 and establishes the method set out in its Schedule (first page; para 1(a)-(b)). The instrument is dated and signed on 12 February 1997 by the General Manager, Flying Operations Branch, a delegate of CASA (first page).

The Determination does not set out any subsequent amendments, modifications, or later revocations within its text. There are no schedules showing later changes or replacement text. The instrument therefore presents a single-stage update to the earlier instrument SRS 2/1992 and stands, as recorded in this text, as the operative method from the date of signing.

Because the Determination itself does not include a history of later amendments, and because the text provided here contains no further amendment entries, the authoritative amendment record that exists within this document is limited to:

• Revocation of SRS 2/1992 (first page; para 1(a)).

• Entry into force as a Determination under paragraph 178(1)(b) of the Civil Aviation Regulations, executed on 12 February 1997 (first page).

The Determination does not provide a schedule of transitional provisions, grandfathering rules, or saving clauses for actions taken under the revoked SRS 2/1992. It does not record whether any previous LSALTs determined under SRS 2/1992 remain effective; it simply revokes the instrument and prescribes the new method for future determinations. Any legacy treatment of previously determined LSALTs would need to be located in the enabling Regulations, other instruments, or administrative guidance outside this Determination.

Given the narrow textual record in this instrument, practitioners should treat the revocation of SRS 2/1992 and the adoption of the schedule-method on 12 February 1997 as the sole amendment history contained herein.

The Determination contains no references to litigation, judicial review, or dispute resolution within its text. It is a technical methodology instrument and does not recount any court cases, appeals, or challenges. The schedule and the main body do not mention any past litigation concerning SRS 2/1992 or the subject matter of LSALT calculation.

Because the text supplied is limited to the Determination itself, and because the Determination does not record any dispute history, there is no litigation history contained in or referenced by this instrument. Any litigation or administrative review concerning the making, application, or consequences of this Determination would have to be identified from sources external to this instrument. The instrument itself neither describes nor documents any legal challenges.

The Determination is prescriptive but contains several technical features and structural choices that may generate practical pitfalls for those who must apply it. Each "gotcha" below is drawn directly from the wording and structure of the instrument.

1. Two alternative pathways, and the precedence of the Grid method: paragraph 2.1 is stated "subject to paragraph 2.2", which means that when the LSALT "is to be determined by reference to Grid LSALTs" the Grid rule in paragraph 2.2 takes precedence over the calculation rule in paragraph 2.1. Users must be explicit about which pathway is being used; an incorrect choice of pathway can yield materially different results because Grid LSALT uses published grid values whereas the non-Grid pathway requires raw terrain/obstacle computations (paras 2.1-2.2, 3.1-3.2).

2. Rounding rule applies to the non-Grid pathway only: paragraph 2.1 requires rounding up to the next 100 feet. Paragraph 2.2 provides the LSALT as "the highest grid LSALT shown for the effective area" and does not restate the rounding rule. Practitioners should note that 2.1’s rounding provision is explicitly attached to the non-Grid calculation pathway and will not necessarily govern Grid LSALTs which are pre-published chart values (paras 2.1-2.2).

3. The 1,500 feet MSL floor can dominate: the required comparison in para 2.1(c) means that where terrain and obstacles are low, the LSALT will default to at least 1,500 feet above mean sea level. That floor is explicit and must be compared against computed terrain/obstacle-derived altitudes (para 2.1(c)).

4. Corrected highest terrain adds 360 feet and includes contour interval: when using a topographical chart, corrected highest terrain is the higher of (a) highest spot height + 360 feet, or (b) highest contour + contour interval + 360 feet. The formula therefore requires knowledge of the chart’s contour interval and spot heights. Omitting the contour interval or misreading it will misstate the corrected terrain (para 4.1).

5. The navigation tolerance area is geometry-driven and depends on operational choices: the shape and extent of the navigation tolerance area differ depending on whether a navigation aid is used at the start of the route segment (angles 10.3° vs 15°), whether an area navigation system is used (distance limits of 30 vs 50 miles), and the rated coverage at the end of the segment (paras 5.2(a)-(c)). Small operational decisions (for example, whether an area navigation system is declared as being used) therefore change the effective area and hence the LSALT.

6. Rated coverage of VOR is capped: for VOR-served segments the rated coverage to be used in the geometric tests is 60 miles or the ERSA-published coverage for the route segment, whichever is less (para 5.3). Practitioners must consult ERSA to determine the coverage that applies and then cap it at 60 miles if ERSA shows a greater number.

7. The effective area differs significantly between Grid and non-Grid methods: when Grid LSALTs are used the effective area is the set of grid squares touched by the navigation tolerance area; when Grid is not used the effective area is the navigation tolerance area plus a 5-mile buffer (paras 3.1-3.2). That 5-mile buffer is easy to overlook but expands the terrain/obstacle population to be checked.

8. Complexity at the end of the segment: paragraph 5.2 contains multiple "whichever happens first" branches and distinct treatments where lines first reach abeam points versus reaching the rated coverage area, plus different treatments where a navigation aid is used at the end of the segment. These conditional branches must be followed in precise order: failing to apply the correct branch can produce an incorrect navigation tolerance area.

9. The Determination presumes availability of chart data and reported obstacles: the non-Grid pathway relies on "highest reported obstacle in the effective area" and corrected highest terrain from aeronautical topographical charts (para 2.1(a) and (b); para 4.1). Absent or out-of-date obstacle reports or topographical charts will undermine the integrity of the calculation; the Determination does not specify data quality standards or update frequency.

10. The Determination revokes SRS 2/1992 but contains no transitional text: the instrument revokes the previous instrument (first page; para 1(a)) but does not contain transitional provisions or guidance about LSALTs previously determined under SRS 2/1992. Practitioners must not assume the instrument leaves previous determinations in place; the text in this instrument does not address that point.

11. The precise angles and distances are non-intuitive: divergence angles of 10.3° and 15° are specific and will require geometric plotting tools; the use of abeam points, semicircles centred on the end of the route segment with radii of 30 or 50 miles, and the use of rated coverage points require careful spatial plotting. Manual approximations are risky.

12. The Determination leaves enforcement questions to other instruments: because there are no penalty or enforcement provisions in the Determination itself, compliance oversight and enforcement will depend on the broader Civil Aviation Act/Regulations and CASA administrative practice, none of which are restated here.

These "gotchas" are drawn directly from the text and structural form of the Determination and should be considered operational constraints and attention items for anyone tasked with performing LSALT determinations under paragraph 178(1)(b).

The Determination prescribes a stepwise calculation method. The following operational checklist recapitulates the method in procedural order and cites the specific paragraphs that require each step. This checklist assumes the practitioner is dealing with a route segment for which LSALT has not been determined under paragraph 178(1)(a).

1. Confirm applicability. Verify that the LSALT for the route segment has not already been determined under paragraph 178(1)(a) of the Civil Aviation Regulations. The Determination applies only where that statutory determination is absent (first page; para 2.1).

2. Decide pathway: Grid LSALT or non-Grid method. Determine whether the LSALT "is to be determined by reference to Grid LSALTs" shown on an ERC or TAC. If that is the intended approach, apply paragraph 2.2 and the Grid pathway; if not, proceed under paragraph 2.1 and the non-Grid pathway (paras 2.1-2.2; para 3.1-3.2).

3. If using the Grid-LSALT pathway (para 2.2 and para 3.1):

   a. Ascertain the navigation tolerance area in accordance with paragraph 5.1 by "applying on either side of the planned track the navigation error allowance appropriate to the navigation aids, system or method used for the navigation of the aircraft" (para 5.1).

   b. Identify all ERC/TAC grid squares that the navigation tolerance area extends over, wholly or in part (para 3.1).

   c. From those grid squares, take the highest Grid LSALT shown on the ERC/TACs; that highest grid value is the LSALT for the route segment (para 2.2, para 3.1).

   d. Check VOR-rated-coverage considerations where the route segment is VOR-served: apply the limitation in paragraph 5.3 (paras 5.1 and 5.3).

4. If using the non-Grid pathway (para 2.1 and para 3.2):

   a. Construct the navigation tolerance area in accordance with paragraph 5.2. Begin at the beginning of the route segment and draw two imaginary lines diverging from the planned track at the beginning:

   • If a navigation aid is used at the beginning of the route segment, use 10.3° divergence; if not, use 15° (para 5.2(a)(i)-(ii)).

   • Continue each line until the first applicable stopping condition described in paragraph 5.2(b)-(f) is reached: abeam the end of the route segment; 30 miles or 50 miles abeam the planned track depending on whether area navigation is used; a point in the rated coverage area of a navigation aid at the end of the route segment from which a straight line to the end would converge at an angle not less than 10.3°, or the particular semicircle/convergence constructions in paras 5.2(d)-(f). Follow the "whichever happens first" ordering set out in para 5.2.

   b. Where the route segment is served by a VOR, determine the rated coverage to be used: take 60 miles or the ERSA-published coverage, whichever is less (para 5.3). Use that coverage when applying the rated-coverage-based stopping rules in paragraph 5.2.

   c. Once the navigation tolerance area is defined, expand it by a 5-mile wide area surrounding the navigation tolerance area to form the effective area (para 3.2(b)).

   d. Determine the highest reported obstacle in the effective area (para 2.1(a)). That requires current obstacle reporting data for the effective area.

   e. If using an aeronautical topographical chart to calculate corrected highest terrain, determine:

   • Highest spot height in the effective area and add 360 feet; and

   • Height of the highest contour in the effective area, add the chart's contour interval (the height between two successive contours) and add 360 feet. The corrected highest terrain is the higher of these two values (para 4.1).

   f. Compute the three candidate altitudes:

   • 1,000 feet above the top of the highest reported obstacle in the effective area (para 2.1(a)).

   • If an aeronautical topographical chart is used, 1,000 feet above the corrected highest terrain (para 2.1(b) and para 4.1).

   • 1,500 feet above mean sea level (para 2.1(c)).

   g. Select the highest of the three candidate altitudes. Round that altitude upward to the next 100 feet (para 2.1).

5. Record and document inputs and assumptions. Although the Determination does not itself specify recordkeeping requirements, compliance requires accurate inputs: the planned track, whether navigation aids are used at the beginning and end of the segment, whether area navigation is used, the navigation error allowances, ERC/TAC grid values, spot heights and contours with contour intervals, reported obstacles in the effective area, and ERSA VOR coverage where relevant (paras 2.1-2.2, 3.1-3.2, 4.1, 5.1-5.3).

6. Check consistency with published charts. If the Grid pathway is used, ensure ERC/TAC grid squares and Grid LSALTs used are the chart editions that the operation relies upon; the Determination ties the Grid method to ERC/TAC published Grid LSALTs (para 3.1).

7. Be explicit about which pathway and which data editions are used. Because the Grid pathway overrides the non-Grid rounding provision and because the navigation tolerance area geometry differs by operational choices (para 2.1-2.2, para 5.2), the user should document which pathway was chosen and why.

8. Apply the VOR coverage cap where relevant. For segments served by a VOR, use 60 miles or the ERSA-published coverage for the route segment, whichever is less (para 5.3).

9. For multi-segment routes, perform the calculation segment-by-segment. The Determination is expressed in terms of route segments; the navigation tolerance area, effective area and resulting LSALT must be determined for each segment to which the regulator’s obligation applies (entire schedule structure).

10. Where in doubt about whether paragraph 178(1)(a) applies, seek the relevant administrative guidance or legal clarification before applying this Determination. The instrument applies only where 178(1)(a) does not provide an LSALT, so the initial legal classification of the segment’s status under the Regulations is the first compliance gate (first page; paras 2.1-2.2).

These steps align directly to the paragraphs in the Determination and produce a reproducible computation methodology. The Determination requires a mixture of published chart data, obstacle reports and geometrical plotting; compliant practice therefore requires access to up-to-date ERC/TAC products, ERSA VOR coverage information, topographical charts with contour intervals and spot heights, and a reliable way to compute the navigation tolerance geometry.