"الكونيك" الإسقاط: رسم الخرائط "الجزر الكبيرة" "مع "الكورا وتفاصيل

المواسير والتخزين

The selection of the standard parallels is the most critical decision in designing a conic projection, these parallels are chosen to lie within the region being mapped, ideally at roughly one-sixth and five-sixths of the latitudinal extent of the area. Between the standard parallels, the scale is slightly too small (compressed), while outside them, the scale is too large (expanded).

مزايا الإسقاطات الكونية

وتوفر التوقعات الكونية مجموعة فريدة من المزايا التي تجعلها مستصوبة للغاية بالنسبة لمهام محددة في مجال رسم الخرائط، وتكمن قوتها الأساسية في أدائها لمناطق وسط خط العرض التي تتسم بتوجهات شرقية غربية مهيمنة.

• Minimal Distortion Along Standard Parallels:] The most significant advantage is the low level of distortion near the standard parallels. This allows for accurate representation of large landmasses that span many degrees of longitude.
• Balance of Properties:] Many conic projections, such as the Albers Equal-Area Conic, are designed to preserve a specific property (like area) while maintaining a relatively low level of shape distortion. This balance is superior to cylindrical projections for regions outside the tropics.
• Familiar Shapes:] For inhabitants of mid-latitude regions, conic projections produce maps that look intuitively correct. Continents like North America, Europe, and Asia are shown with shapes that are readily recognizable and not excessively extended or skewed, unlike some other projection families.
• Versatility in Application:] The conic family includes specialized projections for specific tasks: equal-area projections for thematic maps, conformal projections for navigation, and equidistant projections for radio and seismic mapping.

حدود ومصادر التمييز

وعلى الرغم من مزاياها الكثيرة، فإن التوقعات المخروطية تنطوي على قيود متأصلة تحد من استخدامها، وأهمها تقييد هو عدم ملاءمة رسم الخرائط العالمية أو المناطق الممتدة من خط الاستواء إلى القطبين.

• Severe Polar Distortion:] In standard conic projections, the North Pole is usually represented as an arc or a point at the apex of the cone, and the South Pole is highly distorted or cannot be shown. This makes them completely unsuitable for world maps or maps of polar regions.
• Increasing Distortion Away from Standard Parallels:] While distortion is low near the standard parallels, it increases rapidly as you move away from them. A map of the entire United States using a single conic projection will show noticeable size and shape distortion in Florida and northern Maine compared to the center of the country.
• Directional Limitations:] Conic projections do not preserve true directions (azimuths) from a central point, unlike azimuthal projected. they are not ideal for mapping regions that are oriented north-south (like Chile or Norway), where a Transverse Mercator projection would perform better.

الأنواع الرئيسية للإسقاطات الكونية

وتتضمن الأسرة المكونية عدة اسقاطات متميزة، وكل منها يحقق غرضا رسميا مختلفا، والأهم من ذلك هو كونية آلبيرت المتساوية في آريا، وكونيك لامبرت كونفورمالي، والإسقاطات المكافئة للمكونات.

Albers Equal-Area Conic Projection

Developed by Heinrich Christian Albers in 1805, this projection is the gold standard for thematic and statistical mapping. As an equal-area projection, it correctly represents the relative sizes of regions, making it indispensable for maps showing population density, vegetation cover, climate zones, or disease prevalence. The Albers projection almost always uses two standard parallels to minimize area distortion across the entire map. While shapes are not perfectly preserved, they are generally well-maintained in the mid-latitudes, avoiding the extreme shape distortion seen in other equal-area projections. The United States Geological Survey (USGS) and the Census Bureau extensively use the Albers Equal-Area Conic for national and continental scale thematic maps. Detailed technical parameters for the Albers projection are available from ESRI.

Lambert Conic Projection

Introduced by Johann Heinrich Lambert in 1772, the Lambert Conformal Conic (LCC) is the most widely used projection for aeronautical charts and other applications where maintaining shape and angles is critical. As a conformal projection, local angles and shapes are accurate over small areas. This property is essential for pilots navigating with sectional charts

الإسقاط الكامن

ويميز هذا الإسقاط عن طريق الحفاظ على مسافات دقيقة على طول الماريديان وواحد أو اثنين من الموازين القياسية، أما أوجه القصور التي تقاس من هذه الخطوط فهي صحيحة إلى الحجم، وفي حين أنها ليست منطقة متساوية ولا مطابقة، فإن ممتلكاتها التي ترصد عن بعد تجعلها مفيدة لتطبيقات محددة، مثل رسم خرائط لمسافات الترددات الملاحية أو الموجات السيزمية من مسافات أعلى أو مسافات خرائطية.

The Polyconic Projection

The Polyconic projection is a more complex variation that does not use a single cone but rather a series of cones, each tangent to the world at a different latitude. Each parallel of latitude is developed independently from its own tangent cone. This projection was the standard for USGS topographic map series for much of the 20th century. Its main advantage is that every parallel is a standard minimizing distortion

التطوير التاريخي للإسقاطات الكونية

تاريخ الإسقاطات المُلتوية مُتداخل جداً مع تاريخ رسم الخرائط الحديثة نفسه، حيث كان مُجمّع الجغرافيا و الفلكي اليوناني ()