Manuale di Cartografia Topografica (Parte IV)

Manuale – Parte 1

Manuale – Parte 2

Manuale – Parte 3

Da una domanda di Flavio Cerroni comincio la quarta parte del manuale di Cartografia dedicata a chiarimenti e precisazioni…

Calcolare l’area di un bacino idrografico con la carta millimetrata…

Puoi consultare il manuale gratuitamente,

oppure fare una piccola donazione (3€ ad esempio) con carta di credito cliccando sul tasto “Donate” nella barra laterale.

Grazie!

conto-i-quadretti
Più difficile a dirsi che a farsi!!! …ma prima leggiamo!

Ciao mi chiamo Flavio, ti scrivo per chiederti una cosa riguardo alla tua pubblicazione che hai fatto su scienzafacile.it.
Ho letto il tuo manuale di topografia ( tutte e 3 le parti pubblicate); lo trovo molto utile ed interessanti però vorrei chiederti una cosa a riguardo di un argomento che non hai citato. Come si calcola l’area di un bacino idrografico con la carta millimetrata?
ti ringrazio per l’attenzione!
Flavio

Ovviamente sono io che devo ringraziare Flavio e le migliaia di utenti che utilizzano il mio manuale dandomi molta soddisfazione, ma ora occupiamoci di questo argomento.

Esistono dei programmi che svolgono questa operazione, ma sono convinto che la ‘versione manuale’ aiuti molto di più a ragionare e successivamente ad utilizzare con maggior cognizione di causa anche quelle digitali…

Il calcolo dell’area di un Bacino Idrografico ha una sua utilità.

Dall’area del bacino si può calcolare il volume di acqua raccolto moltiplicando semplicemente per i mm di acqua caduti durante le precipitazioni. Ovviamente tutto ciò che cadrà in una data area non si trasformerà totalmente in acque a scorrimento superficiale, ma in parte verrà assorbita dal terreno o andrà a far parte della rete idrica sotterranea nel caso ce ne sia una…

Ad esempio, in occasione di importanti precipitazioni saranno molto diverse le conseguenze per le zone percorse da un fiume o occupate da un lago con un enorme o un ridottissimo bacino idrografico.

Mai sentito parlare di straripamento del Garda?

No, ovviamente, perchè l’estensione del suo bacino idrografico è irrisoria rispetto al volume di acqua raccolto nel lago.

Il contrario è ad esempio per il lago Maggiore che ha un bacino idrografico immenso, quindi raccoglie molta più acqua di quella che può ‘sopportare’ e quindi straripa molto spesso.

Ma veniamo al ‘calcolo’. In effetti si tratta di risolvere un semplice problema di geometria e di fare una moltiplicazione. Parlando di geometria, preciso anche che l’area del bacino idrografico sarà l’area di una superficie piana e non considera l’esistenza dei rilievi e quindi l’effettiva area della superficie terrestre in questione.

Dopo aver tracciato il bacino idrografico sulla carta, prendiamo un foglio di carta millimetrata trasparente e ricalchiamo  il bacino…

Abbiamo racchiuso quindi una superficie quantificabile in un numero di quadretti di un millimetro di lato. Tutto sta a contarne quanti ce ne sono e a moltiplicare il loro numero per l’area di bacino che corrisponde ad un quadretto.

Semplice no? Ecco un esempio:

Supponiamo di aver tracciato lo spartiacque di un bacino su una tavoletta IGM 1:25000 come ad esempio questo situato sotto il colle di Cussuna dalle parti di Rhemes Notre Dame (AO).

bacino-carta

Ora lo ricalchiamo su un foglio di carta millimetrata trasparente oppure su un foglio non trasparente premuto sulla finestra come ho fatto io!!!

bacino-millimetrata

Ora non ci resta che contare i quadratini!

Sono 2178! In scala 1:25000, un millimetro quadrato sulla carta millimetrata corrisponde nella realtà a 625 m2, quindi l’area totale del bacino è 1361250 m2 che corrispondono a 1.361250 Km2.

I quadratini però non li ho mica contati uno alla volta!!! Mi sono semplificato un po’ la faccenda assegnando dei valori ai quadrati più grandi da 100 quadratini, poi da 50 e anche da 25. Gli altri li ho contati ad uno ad uno, approssimando un po’, soprattutto quando lo spartiacque tagliava diagonalmente i quadratini!

bacino-millimetrata-conto

 

Puoi consultare il manuale gratuitamente,

oppure fare una piccola donazione (3€ ad esempio) con carta di credito cliccando sul tasto “Donate” nella barra laterale.

We use cookies to personalise content and ads, to provide social media features and to analyse our traffic. We also share information about your use of our site with our social media, advertising and analytics partners.
Cookies settings
Accept
Privacy & Cookie policy
Privacy & Cookies policy
Cookie name Active

Privacy Policy

What information do we collect?

We collect information from you when you register on our site or place an order. When ordering or registering on our site, as appropriate, you may be asked to enter your: name, e-mail address or mailing address.

What do we use your information for?

Any of the information we collect from you may be used in one of the following ways: To personalize your experience (your information helps us to better respond to your individual needs) To improve our website (we continually strive to improve our website offerings based on the information and feedback we receive from you) To improve customer service (your information helps us to more effectively respond to your customer service requests and support needs) To process transactions Your information, whether public or private, will not be sold, exchanged, transferred, or given to any other company for any reason whatsoever, without your consent, other than for the express purpose of delivering the purchased product or service requested. To administer a contest, promotion, survey or other site feature To send periodic emails The email address you provide for order processing, will only be used to send you information and updates pertaining to your order.

How do we protect your information?

We implement a variety of security measures to maintain the safety of your personal information when you place an order or enter, submit, or access your personal information. We offer the use of a secure server. All supplied sensitive/credit information is transmitted via Secure Socket Layer (SSL) technology and then encrypted into our Payment gateway providers database only to be accessible by those authorized with special access rights to such systems, and are required to?keep the information confidential. After a transaction, your private information (credit cards, social security numbers, financials, etc.) will not be kept on file for more than 60 days.

Do we use cookies?

Yes (Cookies are small files that a site or its service provider transfers to your computers hard drive through your Web browser (if you allow) that enables the sites or service providers systems to recognize your browser and capture and remember certain information We use cookies to help us remember and process the items in your shopping cart, understand and save your preferences for future visits, keep track of advertisements and compile aggregate data about site traffic and site interaction so that we can offer better site experiences and tools in the future. We may contract with third-party service providers to assist us in better understanding our site visitors. These service providers are not permitted to use the information collected on our behalf except to help us conduct and improve our business. If you prefer, you can choose to have your computer warn you each time a cookie is being sent, or you can choose to turn off all cookies via your browser settings. Like most websites, if you turn your cookies off, some of our services may not function properly. However, you can still place orders by contacting customer service. Google Analytics We use Google Analytics on our sites for anonymous reporting of site usage and for advertising on the site. If you would like to opt-out of Google Analytics monitoring your behaviour on our sites please use this link (https://tools.google.com/dlpage/gaoptout/)

Do we disclose any information to outside parties?

We do not sell, trade, or otherwise transfer to outside parties your personally identifiable information. This does not include trusted third parties who assist us in operating our website, conducting our business, or servicing you, so long as those parties agree to keep this information confidential. We may also release your information when we believe release is appropriate to comply with the law, enforce our site policies, or protect ours or others rights, property, or safety. However, non-personally identifiable visitor information may be provided to other parties for marketing, advertising, or other uses.

Registration

The minimum information we need to register you is your name, email address and a password. We will ask you more questions for different services, including sales promotions. Unless we say otherwise, you have to answer all the registration questions. We may also ask some other, voluntary questions during registration for certain services (for example, professional networks) so we can gain a clearer understanding of who you are. This also allows us to personalise services for you. To assist us in our marketing, in addition to the data that you provide to us if you register, we may also obtain data from trusted third parties to help us understand what you might be interested in. This ‘profiling’ information is produced from a variety of sources, including publicly available data (such as the electoral roll) or from sources such as surveys and polls where you have given your permission for your data to be shared. You can choose not to have such data shared with the Guardian from these sources by logging into your account and changing the settings in the privacy section. After you have registered, and with your permission, we may send you emails we think may interest you. Newsletters may be personalised based on what you have been reading on theguardian.com. At any time you can decide not to receive these emails and will be able to ‘unsubscribe’. Logging in using social networking credentials If you log-in to our sites using a Facebook log-in, you are granting permission to Facebook to share your user details with us. This will include your name, email address, date of birth and location which will then be used to form a Guardian identity. You can also use your picture from Facebook as part of your profile. This will also allow us and Facebook to share your, networks, user ID and any other information you choose to share according to your Facebook account settings. If you remove the Guardian app from your Facebook settings, we will no longer have access to this information. If you log-in to our sites using a Google log-in, you grant permission to Google to share your user details with us. This will include your name, email address, date of birth, sex and location which we will then use to form a Guardian identity. You may use your picture from Google as part of your profile. This also allows us to share your networks, user ID and any other information you choose to share according to your Google account settings. If you remove the Guardian from your Google settings, we will no longer have access to this information. If you log-in to our sites using a twitter log-in, we receive your avatar (the small picture that appears next to your tweets) and twitter username.

Children’s Online Privacy Protection Act Compliance

We are in compliance with the requirements of COPPA (Childrens Online Privacy Protection Act), we do not collect any information from anyone under 13 years of age. Our website, products and services are all directed to people who are at least 13 years old or older.

Updating your personal information

We offer a ‘My details’ page (also known as Dashboard), where you can update your personal information at any time, and change your marketing preferences. You can get to this page from most pages on the site – simply click on the ‘My details’ link at the top of the screen when you are signed in.

Online Privacy Policy Only

This online privacy policy applies only to information collected through our website and not to information collected offline.

Your Consent

By using our site, you consent to our privacy policy.

Changes to our Privacy Policy

If we decide to change our privacy policy, we will post those changes on this page.
Save settings
Cookies settings